House Sparrow

House Sparrow| Passer domesticus

Printed in March 2009, this print of a female House sparrow was created using enamel paint on paper.

House sparrow info via Wikipedia

House sparrow
Passer domesticus male (15).jpg
Male in Germany
House Sparrow, England - May 09.jpg
Female in England
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Passeridae
Genus: Passer
Species: P. domesticus
Binomial name
Passer domesticus
(Linnaeus, 1758)
PasserDomesticusDistribution.png
  Native range
  Introduced range
Synonyms[2]

Fringilla domestica Linnaeus, 1758
Passer domesticus (Linnaeus, 1758) Brisson, 1760
Pyrgita domestica (Linnaeus, 1758) G. Cuvier, 1817
Passer indicus Jardine and Selby, 1835
Passer arboreus Bonaparte, 1850 (preoccupied)
Passer confucius Bonaparte, 1853
Passer rufidorsalis C. L. Brehm, 1855
Passer engimaticus Zarudny, 1903
Passer ahasvar Kleinschmidt, 1904

The house sparrow (Passer domesticus) is a bird of the sparrow family Passeridae, found in most parts of the world. A small bird, it has a typical length of 16 cm (6.3 in) and a mass of 24–39.5 g (0.85–1.39 oz). Females and young birds are coloured pale brown and grey, and males have brighter black, white, and brown markings. One of about 25 species in the genus Passer, the house sparrow is native to most of Europe, the Mediterranean region, and much of Asia. Its intentional or accidental introductions to many regions, including parts of Australia, Africa, and the Americas, make it the most widely distributed wild bird.

The house sparrow is strongly associated with human habitations, and can live in urban or rural settings. Though found in widely varied habitats and climates, it typically avoids extensive woodlands, grasslands, and deserts away from human development. It feeds mostly on the seeds of grains and weeds, but it is an opportunistic eater and commonly eats insects and many other foods. Its predators include domestic cats, hawks, owls, and many other predatory birds and mammals.

Because of its numbers, ubiquity, and association with human settlements, the house sparrow is culturally prominent. It is extensively, and usually unsuccessfully, persecuted as an agricultural pest, but it has also often been kept as a pet, as well as being a food item and a symbol of lust and sexual potency and commonness and vulgarity. Though it is widespread and abundant, its numbers have declined in some areas. The animal's conservation status is listed as least concern on the IUCN Red List.

Description

Measurements and shape

The house sparrow is typically about 16 cm (6.3 in) long, ranging from 14 to 18 cm (5.5 to 7.1 in).[3] It is a compact bird with a full chest and a large, rounded head. Its bill is stout and conical with a culmen length of 1.1–1.5 cm (0.43–0.59 in), strongly built as an adaptation for eating seeds. Its tail is short, at 5.2–6.5 cm (2.0–2.6 in) long. The wing chord is 6.7–8.9 cm (2.6–3.5 in), and the tarsus is 1.6–2.5 cm (0.63–0.98 in).[4][5] In mass, the house sparrow ranges from 24 to 39.5 g (0.85 to 1.39 oz). Females usually are slightly smaller than males. The median mass on the European continent for both sexes is about 30 g (1.1 oz), and in more southerly subspecies is around 26 g (0.92 oz). Younger birds are smaller, males are larger during the winter, and females are larger during the breeding season.[6] Birds at higher latitudes, colder climates, and sometimes higher altitudes are larger (under Bergmann's rule), both between and within subspecies.[6][7][8][9]

Plumage

Male house sparrows in breeding (left) and nonbreeding (right) plumage

The plumage of the house sparrow is mostly different shades of grey and brown. The sexes exhibit strong dimorphism: the female is mostly buffish above and below, while the male has boldly coloured head markings, a reddish back, and grey underparts.[8] The male has a dark grey crown from the top of its bill to its back, and chestnut brown flanking its crown on the sides of its head. It has black around its bill, on its throat, and on the spaces between its bill and eyes (lores). It has a small white stripe between the lores and crown and small white spots immediately behind the eyes (postoculars), with black patches below and above them. The underparts are pale grey or white, as are the cheeks, ear coverts, and stripes at the base of the head. The upper back and mantle are a warm brown, with broad black streaks, while the lower back, rump and uppertail coverts are greyish brown.[10]

Plumage of female House Sparrow.

The male is duller in fresh nonbreeding plumage, with whitish tips on many feathers. Wear and preening expose many of the bright brown and black markings, including most of the black throat and chest patch, called the "bib" or "badge".[10][11] The badge is variable in width and general size, and may signal social status or fitness. This hypothesis has led to a "veritable 'cottage industry'" of studies, which have only conclusively shown that patches increase in size with age.[12] The male's bill is black in the breeding season and horn (dark grey) during the rest of the year.[3]

A close-up of a male house sparrow's head

The female has no black markings or grey crown. Its upperparts and head are brown with darker streaks around the mantle and a distinct pale supercilium. Its underparts are pale grey-brown. The female's bill is brownish-grey and becomes darker in breeding plumage approaching the black of the male's bill.[3][10]

Juveniles are similar to the adult female, but deeper brown below and paler above, with paler and less defined supercilia. Juveniles have broader buff feather edges, and tend to have looser, scruffier plumage, like moulting adults. Juvenile males tend to have darker throats and white postoculars like adult males, while juvenile female tend to have white throats. However, juveniles cannot be reliably sexed by plumage: some juvenile males lack any markings of the adult male, and some juvenile females have male features. The bills of young birds are light yellow to straw, paler than the female's bill. Immature males have paler versions of the adult male's markings, which can be very indistinct in fresh plumage. By their first breeding season, young birds generally are indistinguishable from other adults, though they may still be paler during their first year.[3][10]

Voice

A male calling in San Francisco
Calls, recorded in England

Most house sparrow vocalisations are variations on its short and incessant chirping call. Transcribed as chirrup, tschilp, or philip, this note is made as a contact call by flocking or resting birds, or by males to proclaim nest ownership and invite pairing. In the breeding season, the male gives this call repetitively, with emphasis and speed, but not much rhythm, forming what is described either as a song or an "ecstatic call" similar to a song.[13][14] Young birds also give a true song, especially in captivity, a warbling similar to that of the European greenfinch.[15]

Aggressive males give a trilled version of their call, transcribed as "chur-chur-r-r-it-it-it-it". This call is also used by females in the breeding season, to establish dominance over males while displacing them to feed young or incubate eggs.[16] House sparrows give a nasal alarm call, the basic sound of which is transcribed as quer, and a shrill chree call in great distress.[17] Another vocalisation is the "appeasement call", a soft quee given to inhibit aggression, usually given between birds of a mated pair.[16] These vocalisations are not unique to the house sparrow, but are shared, with small variations, by all sparrows.[18]

Variation

A male of subspecies P. d. indicus in Kolkata, India
A male of subspecies P. d. parkini at Rajkot, India

Some variation is seen in the 12 subspecies of house sparrows, which are divided into two groups, the Oriental P. d. indicus group, and the Palaearctic P. d. domesticus group. Birds of the P. d. domesticus group have grey cheeks, while P. d. indicus group birds have white cheeks, as well as bright colouration on the crown, a smaller bill, and a longer black bib.[19] The subspecies P. d. tingitanus differs little from the nominate subspecies, except in the worn breeding plumage of the male, in which the head is speckled with black and underparts are paler.[20]P. d. balearoibericus is slightly paler than the nominate, but darker than P. d. bibilicus.[21]P. d. bibilicus is paler than most subspecies, but has the grey cheeks of P. d. domesticus group birds. The similar P. d. persicus is paler and smaller, and P. d. niloticus is nearly identical but smaller.[20] Of the less widespread P. d. indicus group subspecies, P. d. hyrcanus is larger than P. d. indicus, P. d. hufufae is paler, P. d. bactrianus is larger and paler, and P. d. parkini is larger and darker with more black on the breast than any other subspecies.[20][22][23]

Identification

The house sparrow can be confused with a number of other seed-eating birds, especially its relatives in the genus Passer. Many of these relatives are smaller, with an appearance that is neater or "cuter", as with the Dead Sea sparrow.[24] The dull-coloured female can often not be distinguished from other females, and is nearly identical to those of the Spanish and Italian sparrows.[10] The Eurasian tree sparrow is smaller and more slender with a chestnut crown and a black patch on each cheek.[25] The male Spanish sparrow and Italian sparrow are distinguished by their chestnut crowns. The Sind sparrow is very similar but smaller, with less black on the male's throat and a distinct pale supercilium on the female.[10]

Taxonomy and systematics

Names

The house sparrow was among the first animals to be given a scientific name in the modern system of biological classification, since it was described by Carl Linnaeus, in the 1758 10th edition of Systema Naturae. It was described from a type specimen collected in Sweden, with the name Fringilla domestica.[26][27] Later, the genus name Fringilla came to be used only for the common chaffinch and its relatives, and the house sparrow has usually been placed in the genus Passer created by French zoologist Mathurin Jacques Brisson in 1760.[28][29]

The bird's scientific name and its usual English name have the same meaning. The Latin word passer, like the English word "sparrow", is a term for small active birds, coming from a root word referring to speed.[30][31] The Latin word domesticus means "belonging to the house", like the common name a reference to its association with humans.[32] The house sparrow is also called by a number of alternative English names, including English sparrow, chiefly in North America;[33][34] and Indian sparrow or Indian house sparrow, for the birds of the Indian subcontinent and Central Asia.[35] Dialectal names include sparr, sparrer, spadger, spadgick, and philip, mainly in southern England; spug and spuggy, mainly in northern England; spur and sprig, mainly in Scotland;[36][37] and spatzie or spotsie, from the German Spatz, in North America.[38]

Taxonomy

A pair of Italian sparrows, in Rome

The genus Passer contains about 25 species, depending on the authority, 26 according to the Handbook of the Birds of the World.[39] Most Passer species are dull-coloured birds with short, square tails and stubby, conical beaks, between 11 and 18 cm (4.3 and 7.1 in) long.[8][40]Mitochondrial DNA studies suggest that speciation in the genus occurred during the Pleistocene and earlier, while other evidence suggests speciation occurred 25,000 to 15,000 years ago.[41][42] Within Passer, the house sparrow is part of the "Palaearctic black-bibbed sparrows" group and a close relative of the Mediterranean "willow sparrows".[39][43]

The taxonomy of the house sparrow and its Mediterranean relatives is highly complicated. The common type of "willow sparrow" is the Spanish sparrow, which resembles the house sparrow in many respects.[44] It frequently prefers wetter habitats than the house sparrow, and it is often colonial and nomadic.[45] In most of the Mediterranean, one or both species occur, with some degree of hybridisation.[46] In North Africa, the two species hybridise extensively, forming highly variable mixed populations with a full range of characters from pure house sparrows to pure Spanish sparrows.[47][48][49]

In much of Italy, a form apparently intermediate between the house and Spanish sparrows, is known as the Italian sparrow. It resembles a hybrid between the two species, and is in other respects intermediate. Its specific status and origin are the subject of much debate.[48][50] In the Alps, the Italian sparrow intergrades over a roughly 20 km (12 mi) strip with the house sparrow,[51] but to the south it intergrades over the southern half of Italy and some Mediterranean islands with the Spanish sparrow.[48] On the Mediterranean islands of Malta, Gozo, Crete, Rhodes, and Karpathos, the other apparently intermediate birds are of unknown status.[48][52][53]

Subspecies

A male of subspecies P. d. balearoibericus in Istanbul
A male of the migratory subspecies P. d. bactrianus (with a Eurasian tree sparrow and young house or Spanish sparrows) in Baikonur, Kazakhstan

A large number of subspecies have been named, of which 12 were recognised in the Handbook of the Birds of the World. These subspecies are divided into two groups, the Palaearctic P. d. domesticus group, and the Oriental P. d. indicus group.[39] Several Middle Eastern subspecies, including P. d. biblicus, are sometimes considered a third, intermediate group. The subspecies P. d. indicus was described as a species, and was considered to be distinct by many ornithologists during the 19th century.[19]

Migratory birds of the subspecies P. d. bactrianus in the P. d. indicus group were recorded overlapping with P. d. domesticus birds without hybridising in the 1970s, so the Soviet scientists Edward I. Gavrilov and M. N. Korelov proposed the separation of the P. d. indicus group as a separate species.[28][54] However, P. d. indicus-group and P. d. domesticus-group birds intergrade in a large part of Iran, so this split is rarely recognised.[39]

In North America, house sparrow populations are more differentiated than those in Europe.[7] This variation follows predictable patterns, with birds at higher latitudes being larger and those in arid areas being paler.[8][55][56] However, how much this is caused by evolution or by environment is not clear.[57][58][59][60] Similar observations have been made in New Zealand,[61] and in South Africa.[62] The introduced house sparrow populations may be distinct enough to merit subspecies status, especially in North America and southern Africa,[39] and American ornithologist Harry Church Oberholser even gave the subspecies name P. d. plecticus to the paler birds of western North America.[55]

P. d. domesticus group
P. d. indicus group
  • P. d. hyrcanus Zarudny and Kudashev, 1916, described from Gorgan, Iran, is found along the southern coast of the Caspian Sea from Gorgan to south-eastern Azerbaijan. It intergrades with P. d. persicus in the Alborz mountains, and with P. d. bibilicus to the west. It is the subspecies with the smallest range.[39][63]
  • P. d. bactrianus Zarudny and Kudashev, 1916, described from Tashkent, is found in southern Kazakhstan to the Tian Shan and northern Iran and Afghanistan. It intergrades with persicus in Baluchistan and with indicus across central Afghanistan. Unlike most other house sparrow subspecies, it is almost entirely migratory, wintering in the plains of the northern Indian subcontinent. It is found in open country rather than in settlements, which are occupied by the Eurasian tree sparrow in its range.[39][63] There is an exceptional record from Sudan.[64]
  • P. d. parkini Whistler, 1920, described from Srinagar, Kashmir, is found in the western Himalayas from the Pamir Mountains to south-eastern Nepal. It is migratory, like P. d. bactrianus.[19][63]
  • P. d. indicus Jardine and Selby, 1831, described from Bangalore, is found in the Indian subcontinent south of the Himalayas, in Sri Lanka, western Southeast Asia, eastern Iran, south-western Arabia and southern Israel.[19][39][63]
  • P. d. hufufae Ticehurst and Cheeseman, 1924, described from Hofuf in Saudi Arabia, is found in north-eastern Arabia.[63][66]
  • P. d. rufidorsalis C. L. Brehm, 1855, described from Khartoum, Sudan, is found in the Nile valley from Wadi Halfa south to Renk in northern South Sudan,[63][64] and in eastern Sudan, northern Ethiopia to the Red Sea coast in Eritrea.[39] It has also been introduced to Mohéli in the Comoros.[67]

Distribution and habitat

By a nest in a saguaro cactus in Arizona
House sparrows perching on a roof, during winter in the Southern Alps of New Zealand

The house sparrow originated in the Middle East and spread, along with agriculture, to most of Eurasia and parts of North Africa.[68] Since the mid-19th century, it has reached most of the world, chiefly due to deliberate introductions, but also through natural and shipborne dispersal.[69] Its introduced range encompasses most of North America, Central America, southern South America, southern Africa, part of West Africa, Australia, New Zealand, and islands throughout the world.[70] It has greatly extended its range in northern Eurasia since the 1850s,[71] and continues to do so, as was shown by the colonisations around 1990 of Iceland and Rishiri Island, Japan.[72] The extent of its range makes it the most widely distributed wild bird on the planet.[70]

Introductions

The house sparrow has become highly successful in most parts of the world where it has been introduced. This is mostly due to its early adaptation to living with humans, and its adaptability to a wide range of conditions.[73][74] Other factors may include its robust immune response, compared to the Eurasian tree sparrow.[75] Where introduced, it can extend its range quickly, sometimes at a rate over 230 km (140 mi) per year.[76] In many parts of the world, it has been characterised as a pest, and poses a threat to native birds.[77][78] A few introductions have died out or been of limited success, such as those to Greenland and Cape Verde.[79]

The first of many successful introductions to North America occurred when birds from England were released in New York City, in 1852 [80][81] to control the ravages of the linden moth.[82] The house sparrow now occurs from the Northwest Territories to southern Panama,[4] and it is one of the most abundant birds in North America.[77] The house sparrow was first introduced to Australia in 1863 at Melbourne and is common throughout the eastern part of the continent,[79] but has been prevented from establishing itself in Western Australia, where every house sparrow found in the state is killed.[83] House sparrows were introduced in New Zealand in 1859, and from there reached many of the Pacific islands, including Hawaii.[84]

In southern Africa, birds of both the European subspecies P. d. domesticus and the Indian subspecies P. d. indicus were introduced around 1900. Birds of P. d. domesticus ancestry are confined to a few towns, while P. d. indicus birds have spread rapidly, reaching Tanzania in the 1980s. Despite this success, native relatives such as the Cape sparrow also occur in towns, competing successfully with it.[79][85] In South America, it was first introduced near Buenos Aires around 1870, and quickly became common in most of the southern part of the continent. It now occurs almost continuously from Tierra del Fuego to the fringes of the Amazon basin, with isolated populations as far north as coastal Venezuela.[79][86][87]

Habitat

The house sparrow is closely associated with human habitation and cultivation.[88] It is not an obligate commensal of humans as some have suggested: Central Asian house sparrows usually breed away from humans in open country,[89] and birds elsewhere are occasionally found away from humans.[88][90][91] The only terrestrial habitats that the house sparrow does not inhabit are dense forest and tundra. Well adapted to living around humans, it frequently lives and even breeds indoors, especially in factories, warehouses, and zoos.[88] It has been recorded breeding in an English coal mine 640 m (2,100 ft) below ground,[92] and feeding on the Empire State Building's observation deck at night.[93] It reaches its greatest densities in urban centres, but its reproductive success is greater in suburbs, where insects are more abundant.[88][94] On a larger scale, it is most abundant in wheat-growing areas such as the Midwestern United States.[95]

It tolerates a variety of climates, but prefers drier conditions, especially in moist tropical climates.[79][88] It has several adaptations to dry areas, including a high salt tolerance[96] and an ability to survive without water by ingesting berries.[97] In most of eastern Asia, the house sparrow is entirely absent, replaced by the Eurasian tree sparrow.[98] Where these two species overlap, the house sparrow is usually more common than the Eurasian tree sparrow, but one species may replace the other in a manner that ornithologist Maud Doria Haviland described as "random, or even capricious".[99] In most of its range, the house sparrow is extremely common, despite some declines,[100] but in marginal habitats such as rainforest or mountain ranges, its distribution can be spotty.[88]

Behaviour

The house sparrow often bathes in water (at left) or in dust (at right)

Social behaviour

The house sparrow is a very social bird. It is gregarious at all seasons when feeding, often forming flocks with other types of birds.[101] It roosts communally, its nests are usually grouped together in clumps, and it engages in social activities such as dust or water bathing and "social singing", in which birds call together in bushes.[102][103] The house sparrow feeds mostly on the ground, but it flocks in trees and bushes.[102] At feeding stations and nests, female house sparrows are dominant despite their smaller size, and in the reproductive period (usually spring or summer), being dominant, they can fight for males.[104][105]

Sleep and roosting

House sparrows sleep with the bill tucked underneath the scapular feathers.[106] Outside of the reproductive season, they often roost communally in trees or shrubs. Much communal chirping occurs before and after the birds settle in the roost in the evening, as well as before the birds leave the roost in the morning.[102] Some congregating sites separate from the roost may be visited by the birds prior to settling in for the night.[107]

Body maintenance

Dust or water bathing is common and often occurs in groups. Anting is rare.[108] Head scratching is done with the leg over the drooped wing.[107]

Feeding

Female foraging in Germany
Two females feeding on leftover food at a cafe in New Zealand.

As an adult, the house sparrow mostly feeds on the seeds of grains and weeds, but it is opportunistic and adaptable, and eats whatever foods are available.[109] In towns and cities, it often scavenges for food in garbage containers and congregates in the outdoors of restaurants and other eating establishments to feed on leftover food and crumbs. It can perform complex tasks to obtain food, such as opening automatic doors to enter supermarkets,[110] clinging to hotel walls to watch vacationers on their balconies,[111] and nectar robbing kowhai flowers.[112] In common with many other birds, the house sparrow requires grit to digest the harder items in its diet. Grit can be either stone, often grains of masonry, or the shells of eggs or snails; oblong and rough grains are preferred.[113][114]

Several studies of the house sparrow in temperate agricultural areas have found the proportion of seeds in its diet to be about 90%.[109][115][116] It will eat almost any seeds, but where it has a choice, it prefers oats and wheat.[117] In urban areas, the house sparrow feeds largely on food provided directly or indirectly by humans, such as bread, though it prefers raw seeds.[116][118] The house sparrow also eats some plant matter besides seeds, including buds, berries, and fruits such as grapes and cherries.[97][116] In temperate areas, the house sparrow has an unusual habit of tearing flowers, especially yellow ones, in the spring.[119]

Animals form another important part of the house sparrow's diet, chiefly insects, of which beetles, caterpillars, dipteran flies, and aphids are especially important. Various noninsect arthropods are eaten, as are molluscs and crustaceans where available, earthworms, and even vertebrates such as lizards and frogs.[109] Young house sparrows are fed mostly on insects until about 15 days after hatching.[120] They are also given small quantities of seeds, spiders, and grit. In most places, grasshoppers and crickets are the most abundant foods of nestlings.[121]True bugs, ants, sawflies, and beetles are also important, but house sparrows take advantage of whatever foods are abundant to feed their young.[121][122][123] House sparrows have been observed stealing prey from other birds, including American robins.[4]

Locomotion

The house sparrow's flight is direct (not undulating) and flapping, averaging 45.5 km/h (28.3 mph) and about 15 wingbeats per second.[107][124] On the ground, the house sparrow typically hops rather than walks. It can swim when pressed to do so by pursuit from predators. Captive birds have been recorded diving and swimming short distances under water.[107]

Dispersal and migration

Most house sparrows do not move more than a few kilometres during their lifetimes. However, limited migration occurs in all regions. Some young birds disperse long distances, especially on coasts, and mountain birds move to lower elevations in winter.[102][125][126] Two subspecies, P. d. bactrianus and P. d. parkini, are predominantly migratory. Unlike the birds in sedentary populations that migrate, birds of migratory subspecies prepare for migration by putting on weight.[102]

Breeding

A pair of the subspecies P. d. indicus mating in Kolkata

House sparrows can breed in the breeding season immediately following their hatching, and sometimes attempt to do so. Some birds breeding for the first time in tropical areas are only a few months old and still have juvenile plumage.[127] Birds breeding for the first time are rarely successful in raising young, and reproductive success increases with age, as older birds breed earlier in the breeding season, and fledge more young.[128] As the breeding season approaches, hormone releases trigger enormous increases in the size of the sexual organs and changes in day length lead males to start calling by nesting sites.[129][130] The timing of mating and egg-laying varies geographically, and between specific locations and years because a sufficient supply of insects is needed for egg formation and feeding nestlings.[131]

Males take up nesting sites before the breeding season, by frequently calling beside them. Unmated males start nest construction and call particularly frequently to attract females. When a female approaches a male during this period, the male displays by moving up and down while drooping and shivering his wings, pushing up his head, raising and spreading his tail, and showing his bib.[131] Males may try to mate with females while calling or displaying. In response, a female will adopt a threatening posture and attack a male before flying away, pursued by the male. The male displays in front of her, attracting other males, which also pursue and display to the female. This group display usually does not immediately result in copulations.[131] Other males usually do not copulate with the female.[132][133] Copulation is typically initiated by the female giving a soft dee-dee-dee call to the male. Birds of a pair copulate frequently until the female is laying eggs, and the male mounts the female repeatedly each time a pair mates.[131]

The house sparrow is monogamous, and typically mates for life. Birds from pairs often engage in extra-pair copulations, so about 15% of house sparrow fledglings are unrelated to their mother's mate.[134] Male house sparrows guard their mates carefully to avoid being cuckolded, and most extra-pair copulation occurs away from nest sites.[132][135] Males may sometimes have multiple mates, and bigamy is mostly limited by aggression between females.[136] Many birds do not find a nest and a mate, and instead may serve as helpers around the nest for mated pairs, a role which increases the chances of being chosen to replace a lost mate. Lost mates of both sexes can be replaced quickly during the breeding season.[132][137] The formation of a pair and the bond between the two birds is tied to the holding of a nest site, though paired house sparrows can recognise each other away from the nest.[131]

Nesting

Female bringing food for young in a nest made in a tree hole in California

Nest sites are varied, though cavities are preferred. Nests are most frequently built in the eaves and other crevices of houses. Holes in cliffs and banks, or tree hollows, are also used.[138][139] A sparrow sometimes excavates its own nests in sandy banks or rotten branches, but more frequently uses the nests of other birds such as those of swallows in banks and cliffs, and old tree cavity nests.[138] It usually uses deserted nests, though sometimes it usurps active ones.[138][140] Tree hollows are more commonly used in North America than in Europe,[138] putting the sparrows in competition with bluebirds and other North American cavity nesters, and thereby contributing to their population declines.[77]

Especially in warmer areas, the house sparrow may build its nests in the open, on the branches of trees, especially evergreens and hawthorns, or in the nests of large birds such as storks or magpies.[131][138][141] In open nesting sites, breeding success tends to be lower, since breeding begins late and the nest can easily be destroyed or damaged by storms.[138][142] Less common nesting sites include street lights and neon signs, favoured for their warmth; and the old open-topped nests of other songbirds, which are then domed over.[138][139]

The nest is usually domed, though it may lack a roof in enclosed sites.[138] It has an outer layer of stems and roots, a middle layer of dead grass and leaves, and a lining of feathers, as well as of paper and other soft materials.[139] Nests typically have external dimensions of 20 × 30 cm (8 × 12 in),[131] but their size varies greatly.[139] The building of the nest is initiated by the unmated male while displaying to females. The female assists in building, but is less active than the male.[138] Some nest building occurs throughout the year, especially after moult in autumn. In colder areas house sparrows build specially created roost nests, or roost in street lights, to avoid losing heat during the winter.[138][143] House sparrows do not hold territories, but they defend their nests aggressively against intruders of the same sex.[138]

House sparrows' nests support a wide range of scavenging insects, including nest flies such as Neottiophilum praestum, Protocalliphora blowflies,[144][145] and over 1,400 species of beetle.[146]

Eggs and young

Eggs in a nest

Clutches usually comprise four or five eggs, though numbers from one to 10 have been recorded. At least two clutches are usually laid, and up to seven a year may be laid in the tropics or four a year in temperate latitudes. When fewer clutches are laid in a year, especially at higher latitudes, the number of eggs per clutch is greater. Central Asian house sparrows, which migrate and have only one clutch a year, average 6.5 eggs in a clutch. Clutch size is also affected by environmental and seasonal conditions, female age, and breeding density.[147][148]

Naked and blind chick
A hatchling

Some intraspecific brood parasitism occurs, and instances of unusually large numbers of eggs in a nest may be the result of females laying eggs in the nests of their neighbours. Such foreign eggs are sometimes recognised and ejected by females.[147][149] The house sparrow is a victim of interspecific brood parasites, but only rarely, since it usually uses nests in holes too small for parasites to enter, and it feeds its young foods unsuitable for young parasites.[150][151] In turn, the house sparrow has once been recorded as a brood parasite of the American cliff swallow.[149][152]

A juvenile, showing its pink bill and obvious nestling gape—the soft, swollen base, which becomes harder and less swollen as the bird matures

The eggs are white, bluish white, or greenish white, spotted with brown or grey.[107] Subelliptical in shape,[8] they range from 20 to 22 mm (0.79 to 0.87 in) in length and 14 to 16 mm (0.55 to 0.63 in) in width,[4] have an average mass of 2.9 g (0.10 oz),[153] and an average surface area of 9.18 cm2 (1.423 in2).[154] Eggs from the tropical subspecies are distinctly smaller.[155][156] Eggs begin to develop with the deposition of yolk in the ovary a few days before ovulation. In the day between ovulation and laying, egg white forms, followed by eggshell.[157] Eggs laid later in a clutch are larger, as are those laid by larger females, and egg size is hereditary. Eggs decrease slightly in size from laying to hatching.[158] The yolk comprises 25% of the egg, the egg white 68%, and the shell 7%. Eggs are watery, being 79% liquid, and otherwise mostly protein.[159]

The female develops a brood patch of bare skin and plays the main part in incubating the eggs. The male helps, but can only cover the eggs rather than truly incubate them. The female spends the night incubating during this period, while the male roosts near the nest.[147] Eggs hatch at the same time, after a short incubation period lasting 11–14 days, and exceptionally for as many as 17 or as few as 9.[8][131][160] The length of the incubation period decreases as ambient temperature increases later in the breeding season.[161]

A female feeding a fledgling

Young house sparrows remain in the nest for 11 to 23 days, normally 14 to 16 days.[107][161][162] During this time, they are fed by both parents. As newly hatched house sparrows do not have sufficient insulation, they are brooded for a few days, or longer in cold conditions.[161][163] The parents swallow the droppings produced by the hatchlings during the first few days; later, the droppings are moved up to 20 m (66 ft) away from the nest.[163][164]

The chicks' eyes open after about four days and, at an age of about eight days, the young birds get their first down.[107][162] If both parents perish, the ensuing intensive begging sounds of the young often attract replacement parents which feed them until they can sustain themselves.[163][165] All the young in the nest leave it during the same period of a few hours. At this stage, they are normally able to fly. They start feeding themselves partly after one or two days, and sustain themselves completely after 7 to 10 days, 14 at the latest.[166]

Survival

In adult house sparrows, annual survival is 45–65%.[167] After fledging and leaving the care of their parents, young sparrows have a high mortality rate, which lessens as they grow older and more experienced. Only about 20–25% of birds hatched survive to their first breeding season.[168] The oldest known wild house sparrow lived for nearly two decades; it was found dead 19 years and 9 months after it was ringed in Denmark.[169] The oldest recorded captive house sparrow lived for 23 years.[170] The typical ratio of males to females in a population is uncertain due to problems in collecting data, but a very slight preponderance of males at all ages is usual.[171]

Predation

A male being eaten by a cat: Domestic cats are one of the main predators of the house sparrow.

The house sparrow's main predators are cats and birds of prey, but many other animals prey on them, including corvids, squirrels,[172] and even humans—the house sparrow has been consumed in the past by people in many parts of the world, and it still is in parts of the Mediterranean.[173] Most species of birds of prey have been recorded preying on the house sparrow in places where records are extensive. Accipiters and the merlin in particular are major predators, though cats are likely to have a greater impact on house sparrow populations.[172] The house sparrow is also a common victim of roadkill; on European roads, it is the bird most frequently found dead.[174]

Parasites and disease

The house sparrow is host to a huge number of parasites and diseases, and the effect of most is unknown. Ornithologist Ted R. Anderson listed thousands, noting that his list was incomplete.[175] The commonly recorded bacterial pathogens of the house sparrow are often those common in humans, and include Salmonella and Escherichia coli.[176]Salmonella is common in the house sparrow, and a comprehensive study of house sparrow disease found it in 13% of sparrows tested. Salmonella epidemics in the spring and winter can kill large numbers of sparrows.[175] The house sparrow hosts avian pox and avian malaria, which it has spread to the native forest birds of Hawaii.[177] Many of the diseases hosted by the house sparrow are also present in humans and domestic animals, for which the house sparrow acts as a reservoir host.[178]Arboviruses such as the West Nile virus, which most commonly infect insects and mammals, survive winters in temperate areas by going dormant in birds such as the house sparrow.[175][179] A few records indicate disease extirpating house sparrow populations, especially from Scottish islands, but this seems to be rare.[180]

The house sparrow is infested by a number of external parasites, which usually cause little harm to adult sparrows. In Europe, the most common mite found on sparrows is Proctophyllodes, the most common ticks are Argas reflexus and Ixodes arboricola, and the most common flea on the house sparrow is Ceratophyllus gallinae. A number of chewing lice occupy different niches on the house sparrow's body. Menacanthus lice occur across the house sparrow's body, where they feed on blood and feathers, while Brueelia lice feed on feathers and Philopterus fringillae occurs on the head.[144]

Physiology

House sparrows express strong circadian rhythms of activity in the laboratory. They were among the first bird species to be seriously studied in terms of their circadian activity and photoperiodism, in part because of their availability and adaptability in captivity, but also because they can "find their way" and remain rhythmic in constant darkness.[181][182] Such studies have found that the pineal gland is a central part of the house sparrow's circadian system: removal of the pineal eliminates the circadian rhythm of activity,[183] and transplant of the pineal into another individual confers to this individual the rhythm phase of the donor bird.[184] The suprachiasmatic nuclei of the hypothalamus have also been shown to be an important component of the circadian system of house sparrows.[185] The photoreceptors involved in the synchronisation of the circadian clock to the external light-dark cycle are located in the brain and can be stimulated by light reaching them directly though the skull, as revealed by experiments in which blind sparrows, which normally can still synchronise to the light-dark cycle, failed to do so once India ink was injected as a screen under the skin on top of their skulls.[186]

Similarly, even when blind, house sparrows continue to be photoperiodic, i.e. show reproductive development when the days are long, but not when the days are short. This response is stronger when the feathers on top of the head are plucked, and is eliminated when India ink is injected under the skin at the top of the head, showing that the photoreceptors involved in the photoperiodic response to day length are located inside the brain.[187]

House sparrows have also been used in studies of nonphotic entrainment (i.e. synchronisation to an external cycle other than light and dark): for example, in constant darkness, a situation in which the birds would normally reveal their endogenous, non-24-hour, "free-running" rhythms of activity, they instead show 24-hour periodicity if they are exposed to two hours of chirp playbacks every 24 hours, matching their daily activity onsets with the daily playback onsets.[188] House sparrows in constant dim light can also be entrained to a daily cycle based on the presence of food.[189] Finally, house sparrows in constant darkness can be entrained to a cycle of high and low temperature, but only if the difference between the two temperatures is large (38 versus 6 °C); some of the tested sparrows matched their activity to the warm phase, and others to the cold phase.[190]

Relationships with humans

Flocking and chirping together beneath a fluorescent tube light in Germany

The house sparrow is closely associated with humans. They are believed to have become associated with humans around 10,000 years ago. Subspecies P. d. bactrianus is least associated with humans and considered to be evolutionarily closer to the ancestral noncommensal populations.[191] Usually, it is regarded as a pest, since it consumes agricultural products and spreads disease to humans and their domestic animals.[192] Even birdwatchers often hold it in little regard because of its molestation of other birds.[77] In most of the world, the house sparrow is not protected by law. Attempts to control house sparrows include the trapping, poisoning, or shooting of adults; the destruction of their nests and eggs; or less directly, blocking nest holes and scaring off sparrows with noise, glue, or porcupine wire.[193] However, the house sparrow can be beneficial to humans, as well, especially by eating insect pests, and attempts at the large-scale control of the house sparrow have failed.[39]

The house sparrow has long been used as a food item. From around 1560 to at least the 19th century in northern Europe, earthenware "sparrow pots" were hung from eaves to attract nesting birds so the young could be readily harvested. Wild birds were trapped in nets in large numbers, and sparrow pie was a traditional dish, thought, because of the association of sparrows with lechery, to have aphrodisiac properties. Sparrows were also trapped as food for falconers' birds and zoo animals. In the early part of the 20th century, sparrow clubs culled many millions of birds and eggs in an attempt to control numbers of this perceived pest, but with only a localised impact on numbers.[194] House sparrows have been kept as pets at many times in history, though they have no bright plumage or attractive songs, and raising them is difficult.[195]

Status

The house sparrow has an extremely large range and population, and is not seriously threatened by human activities, so it is assessed as least concern for conservation on the IUCN Red List.[1] However, populations have been declining in many parts of the world.[196][197][198] These declines were first noticed in North America, where they were initially attributed to the spread of the house finch, but have been most severe in Western Europe.[199][200] Declines have not been universal, as no serious declines have been reported from Eastern Europe, but have even occurred in Australia, where the house sparrow was introduced recently.[201]

In Great Britain, populations peaked in the early 1970s,[202] but have since declined by 68% overall,[203] and about 90% in some regions.[204][205] In London, the house sparrow almost disappeared from the central city.[204] The numbers of house sparrows in the Netherlands have dropped in half since the 1980s,[94] so the house sparrow is even considered an endangered species.[206] This status came to widespread attention after a female house sparrow, referred to as the "Dominomus", was killed after knocking down dominoes arranged as part of an attempt to set a world record.[207] These declines are not unprecedented, as similar reductions in population occurred when the internal combustion engine replaced horses in the 1920s and a major source of food in the form of grain spillage was lost.[208][209]

Various causes for the dramatic decreases in population have been proposed, including predation, in particular by Eurasian sparrowhawks;[210][211][212] electromagnetic radiation from mobile phones;[213] and diseases.[214] A shortage of nesting sites caused by changes in urban building design is probably a factor, and conservation organisations have encouraged the use of special nest boxes for sparrows.[214][215][216][217][218][unreliable source?] A primary cause of the decline seems to be an insufficient supply of insect food for nestling sparrows.[214][219] Declines in insect populations result from an increase of monoculture crops, the heavy use of pesticides,[220][221][222] the replacement of native plants in cities with introduced plants and parking areas,[223][224] and possibly the introduction of unleaded petrol, which produces toxic compounds such as methyl nitrite.[225]

Protecting insect habitats on farms,[226][227] and planting native plants in cities benefit the house sparrow, as does establishing urban green spaces.[228][229] To raise awareness of threats to the house sparrow, World Sparrow Day has been celebrated on 20 March across the world since 2010.[230] Over the recent years, the house sparrow population has been on the decline in many Asian countries, and this decline is quite evident in India. To promote the conservation of these birds, in 2012, the then Chief Minister of Delhi, Ms. Sheila Dikshit, declared the house sparrow as the state bird of Delhi.[231][232]

Cultural associations

To many people across the world, the house sparrow is the most familiar wild animal and, because of its association with humans and familiarity, it is frequently used to represent the common and vulgar, or the lewd.[233] One of the reasons for the introduction of house sparrows throughout the world was their association with the European homeland of many immigrants.[81] Birds usually described later as sparrows are referred to in many works of ancient literature and religious texts in Europe and western Asia. These references may not always refer specifically to the house sparrow, or even to small, seed-eating birds, but later writers who were inspired by these texts often had the house sparrow in mind.[39][233][234] In particular, sparrows were associated by the ancient Greeks with Aphrodite, the goddess of love, due to their perceived lustfulness, an association echoed by later writers such as Chaucer and Shakespeare.[39][195][233][235] Jesus's use of "sparrows" as an example of divine providence in the Gospel of Matthew[236] also inspired later references, such as that in Shakespeare's Hamlet[233] and the Gospel hymn His Eye Is on the Sparrow.[237]

G37
The house sparrow is only represented in ancient Egyptian art very rarely, but an Egyptian hieroglyph is based on it. The sparrow hieroglyph had no phonetic value and was used as a determinative in words to indicate small, narrow, or bad.[238] An alternative view is that the hieroglyph meant "a prolific man" or "the revolution of a year".[239]

See also

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Works cited

External links

source: http://en.wikipedia.org/wiki/House_sparrow

Austin Art Board Submission

Would you like to see these inked animals on Billboards around Austin?

Urban Birds of Austin

Mexican Free-tailed Bat 1
Adam and I, coerced by our friend Hayley of the Biocreativity Blog, decided to enter into the Austin Art Board contest this year.  Only one submission per person, so Adam and I individually created a unique take on some of our prints.  I kept it simple, using the Mexican Freetail bat as my subject.  I thought it would be a nice specimen considering Austin’s love affair with this critter. Adam got a bit more creative, and did a  bit of a collage of a few birds, most of which we haven’t posted yet (we have tons of material coming soon).

 

 

 

Alligator Gar

Alligator Gar | Atractosteus spatula

 

We have to give some credit to Robby Maxwell here.  He aided with both the capture and immortalization of this beast.  It wasn’t the largest Alligator gar we’d seen, but large enough and a great time to catch. Robby, myself, and a large Texas State University crew wrangled this specimen as part of my master’s thesis working on the Brazos River watershed, Texas.  He’ll have to confirm, but I believe we caught this in the winter of 2008 in Brazos Bend State Park under the watchful gaze of park authority and many reptilian versions of alligators. This gyotaku print will surely be popular among many fish fanatics that I know who, justifiably so, respect the hell out of this fish. This species is known to get massive, one of the largest freshwater predators in the world.  Its even been featured on River Monsters I believe.  Its also a very old lineage of fish with a special version of a circulatory system that relies on oxygen brought in not just through its gills, but also through its toothy mug into its air bladder where gas exchange occurs.  For this reason, gar are one of those few fish that you can actually drown!


Alligator Gar info via Wikipedia:

Alligator gar
Alligator Gar 10.JPG
Alligator gar in an aquarium
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Lepisosteiformes
Family: Lepisosteidae
Genus: Atractosteus
Species: A. spatula
Binomial name
Atractosteus spatula
(Lacépède, 1803)
Atractosteus spatula range.png
Synonyms
  • Lepisosteus spatula Lacépède, 1803
  • Atractosteus adamantinus Rafinesque, 1818
  • Atractosteus lucius Duméril, 1870
  • Esox cepedianus Shaw, 1804
  • Lepisosteus berlandieri Girard, 1858
  • Lepisosteus ferox Rafinesque, 1820
  • Litholepis adamantinus Rafinesque, 1818

Alligator gar (Atractosteus spatula) are ray-finned euryhaline fish related to bowfin in the infraclass Holostei (ho'-las-te-i). The fossil record traces their existence to the Early Cretaceous over a hundred million years ago. They are the largest species in the gar family, and among the largest freshwater fishes in North America. Gars are often referred to as "primitive fishes", or "living fossils" because they have retained some morphological characteristics of their earliest ancestors, such as a spiral valve intestine which is also common to the digestive system of sharks, and the ability to breathe both air and water. Their common name was derived from their resemblance to American alligator, particularly their broad snout and long sharp teeth. Anecdotal evidence in several scientific reports suggest that an alligator gar can grow up to 10 ft (3.0 m) in length and weigh as much as 300 lb (140 kg); however in 2011 the largest alligator gar ever caught and officially recorded was 8 ft 5 14 in (2.572 m) long, weighed 327 lb (148 kg), and was 47 in (120 cm) around the girth.

The body of an alligator gar is torpedo shaped, usually brown or olive fading to a lighter gray or yellow ventral surface. Their scales are not like the scales of other fishes; rather, they are ganoid scales which are bone-like, diamond-shaped scales, often with serrated edges, and covered by an enamel-like substance. Ganoid scales are nearly impenetrable and are excellent protection against predation. Unlike other gar species, the upper jaw of an alligator gar has a dual row of large sharp teeth which are used to impale and hold prey. Alligator gar are stalking, ambush predators, primarily piscivores, but they will also ambush and eat water fowl and small mammals they find floating on the water's surface.

Populations of alligator gar have been extirpated from much of their historic range as a result of habitat destruction, indiscriminate culling, and unrestricted harvests. Populations are now located primarily in the southern portions of the United States extending into Mexico. They are considered euryhaline because they can adapt to varying salinities ranging from freshwater lakes and swamps to brackish marshes, estuaries, and bays along the Gulf of Mexico.

For nearly a half-century, alligator gar were considered "trash fish",[1] or a "nuisance species" detrimental to sport fisheries; therefore, were targeted for elimination by state and federal authorities in the United States. The 1980s brought a better understanding of the ecological balance necessary to sustain an ecosystem,[2] and eventually an awareness that alligator gar were no less important than any other living organism in the ecosystems they inhabit.[3] Over time, alligator gar were afforded some protection by state and federal resource agencies. They are also protected under the Lacey Act which makes it illegal to transport certain species of fish in interstate commerce when in violation of state law or regulation. Several state and federal resource agencies are monitoring populations in the wild, and have initiated outreach programs to educate the public. Alligator gar are being cultured in ponds, pools, raceways and tanks by federal hatcheries for mitigation stocking, by universities for research purposes, and in Mexico for consumption.[4]

Anatomy

Preserved display of an alligator gar head

Alligator gar are the largest species in the gar family, and among the largest freshwater fishes found in North America. Mature alligator gar commonly measure 6 ft (1.8 m) in length, and weigh over 100 lbs. (45 kg). However, anecdotal reports suggest they can grow up to 10 ft (3m) in length, and weigh as much as 350 lbs. (159 kg).[5] The largest alligator gar officially recorded was inadvertently caught in the net of fisherman Kenny Williams of Vicksburg, Mississippi while he was fishing the oxbow lakes of the Mississippi River on February 14, 2011. Williams was pulling up his net on Lake Chotard expecting to find buffalo fish, but instead discovered a large alligator gar tangled in his net. The gar was 8 ft 5 14 in (2.572 m) long, weighed 327 lb (148 kg), and its girth was 47 in (120 cm). According to wildlife officials, the fish was estimated to be somewhere between 50 and 70 years old; one report estimated the gar's age to be at least 95.[6] Williams donated it to the Mississippi Museum of Natural Science in Jackson where it will remain on display.[7][8]

Gill of a juvenile gar

All gars have torpedo-shaped bodies, but some distinguishing characteristics of adult alligator gar include their large size, heavy bodies, broad heads, short broad snouts, large sharp teeth and double row of teeth on their upper jaw. They are usually brown or olive fading to a lighter gray or yellow ventral surface. The dorsal and anal fins are positioned toward the back of their bodies, and their caudal fin is abbreviate-heterocercal, or non-symmetrical.[5]

Physiology

Alligator gar have gills, but unlike other species of fish, with few exceptions, they also have a highly vascularized swim bladder lung that supplements gill respiration.[9] The bladder not only provides buoyancy but also enables them to breathe in air which is why they are able to inhabit bodies of water in which most other fishes would die of suffocation. The swim bladder is connected to their foregut by a small pneumatic duct which allows them to breathe or gulp air when they break the surface,[10] an action that is seen quite frequently on lakes in the southern United States during the hot summer months. The scales of alligator gar are not like the scales of other fishes which have flexible elasmoid scales; their bodies are protected by inflexible and articulated ganoid scales that are diamond-shaped, often with serrated edges, and composed of a tough inner layer of bone and hard outer layer of ganoin which is essentially homologous to tooth enamel, making them nearly impenetrable.[11][12][13]

Taxonomy and evolution

Lacépède first described the alligator gar in 1803. The original name was Lepisosteus spatula, but was later changed by E.O. Wiley in 1976 to Atractosteus spatula in order to recognize two distinct extant taxon of gars. Synonyms of Atractosteus spatula include Lesisosteus [sic] ferox (Rafinesque 1820), and Lepisosteus spatula (Lacepede 1803). Fossils from the order Lepisosteiformes have been collected in Europe from the Cretaceous to Oligocene periods, in Africa and India from the Cretaceous, and in North America from the Cretaceous to recent times. Lepisosteidae is the only extant family of gar which has seven species all located in North and Central America.[5] The fossil record traces the existence of alligator gar back to the Early Cretaceous over a hundred million years ago.[14][15] Despite being a highly evolved species, alligator gar are often referred to as "primitive fishes", or "living fossils"[16][17] because they have retained a few morphological characteristics of their earliest ancestors with seemingly little to no apparent changes, such as a spiral valve intestine which is also common to the digestive system of sharks, an abbreviate-heterocercal tail, and a swim bladder lung for breathing in both air and water.[5][18][19]

Feeding behavior

Alligator gar are stalking, ambush predators

Alligator gar are relatively passive, seemingly sluggish solitary fish, but voracious ambush predators. They are opportunistic night predators and are primarily piscivores, but they will also ambush and eat water fowl and small mammals that may be floating on the surface. Their method of ambush is to float a few feet below the surface, and wait for unsuspecting prey to swim within reach. They lunge forward, and with a sweeping motion grab their prey, impaling it on their double rows of sharp teeth.[18]

Diet studies have shown alligator gar to be opportunistic piscivores, and even scavengers depending on the availability of their preferred food source. They occasionally ingest sport fish, but the majority of stomach content studies suggest they feed predominately on forage fishes such as gizzard shad as well as invertebrates, and water fowl. Diet studies have also revealed fishing tackle and boat engine parts in their stomachs.[20][21]

Spawning

As with most ancestral species, alligator gar are long living, and sexually late maturing. Most females do not reach sexual maturity until after their first decade of life while males reach sexual maturity in half that time. The conditions must be precise for a successful spawning to occur. Preparation for spawning begins in the spring with the extended photoperiod and rising water temperatures, but flooding is also necessary to trigger the event. When rivers rise and spread over the floodplain, they create oxbow lakes and sloughs, and inundate terrestrial vegetation which in turn provides protection and a nutrient rich habitat for larval fishes, and fry. Once the water temperature has reached 68 to 82 °F (20 to 28 °C), and all the other criteria are met, gars will move into the grassy, weed-laden shallows to spawn.[22][23]

Actual spawning occurs when a collection of males gather around gravid females, and begin writhing, twisting, bumping into and slithering over the tops of females, an activity which triggers the release of eggs. Males release clouds of milt to fertilize the eggs as they are released into the water column.[22] The sticky eggs then attach to submerged vegetation, and development begins. It takes only a few days for the eggs to hatch into larval fish, and another ten days or so for the larval fish to detach from the vegetation and start moving about as young fry.[23] Egg production is variable, and believed to be dependent on the size of the female. A common formula used for predicting the volume of eggs a female can produce is 4.1 eggs/gram of body weight which gives an average of about 150,000 eggs per spawn. The eggs of alligator gar are bright red and poisonous to humans if ingested.[18]

Distribution

Alligator gar caught in Moon Lake, Mississippi, March 1910

Natural range

Alligator gar inhabit a wide variety of aquatic habitats, but most are found in the Southern United States in reservoirs and lakes, in the backwaters of lowland rivers, and in the brackish waters of estuaries, bayous and bays. They have occasionally been seen in the Gulf of Mexico.[18] In Texas and Louisiana it is common to see large gars breaking the surface in reservoirs, bayous, and brackish marshes. They are found throughout the lower Mississippi River Valley and Gulf Coast states of the Southern United States and Mexico as far south as Veracruz, encompassing the following states in the United States: Texas, Oklahoma, Louisiana, Kentucky, Mississippi, Alabama, Tennessee, Arkansas, Missouri, Illinois, Florida, and Georgia.[24] Reports suggest alligator gar were once numerous throughout much of their northern range, however valid sightings today are rare, and may occur once every few years.[5] Records of historical distribution indicate alligator gar once inhabited regions as far north as central Kansas, Nebraska, Ohio, Iowa, and west-central Illinois where they are now listed as extirpated. The most northerly verified catch was in Meredosia, Illinois in 1922.[25] There are now efforts to reintroduce alligator gar between Tennessee and Illinois as part of an effort to control invasive Asian carp.[26]

Outside natural range

A few notable sightings of alligator gar have been reported outside North America. In November 2008, a broadhead gar, genus Atractosteus, measuring 5.2 to 6.4 ft (1.6 to 2.0 m) was caught in the Caspian Sea north of Esenguly, Turkmenistan by two officials of Turkmenistan Fishery Protection.[27] Its species is unconfirmed but is believed to be an alligator gar.[28]

On September 4, 2009 a 3 ft 3 in (0.99 m) alligator gar was found in Tak Wah Park in Tsuen Wan, Hong Kong. Over the next two days, at least 16 other alligator gar, the largest measuring 4.9 ft (1.5 m), were found in ponds in public parks in Hong Kong.[29] Nearby residents reported the alligator gar had been released into the ponds by aquarium hobbyists, and had lived there for several years. However, after a complaint made by a citizen who falsely identified alligator gar as crocodiles, the use of terms like "horrible man-eating fish" had begun appearing in the headlines of some major local newspapers. Officials with Leisure and Cultural Services in Tak Wah Park removed all the alligator gar from the ponds because they were concerned the large, carnivorous fish might harm children.[30] It is not unusual for the large sharp teeth and outward appearance of alligator gar to precipitate unreasonable fear in those unfamiliar with the species. Sensationalized reports have contributed to the misconception of predatory attacks by alligator gar on humans even though none of the reports have been confirmed.[31]

On January 21, 2011, an alligator gar measuring 4 feet 11 inches (1.50 m) was caught in a canal in Pasir Ris, Singapore by two recreational fishermen. The fish was taken to a nearby pond where the owner confirmed it was an alligator gar rather than an arapaima as the men had initially thought.[32]

There have been anecdotal reports of alligator gar captured in various parts of India but are believed to be the result of incidental releases by aquarium hobbyists and the like. In August 2015, an alligator gar was found entangled in cloth inside a well in Dadar where it had been living for quite some time. It was rescued by animal activists and returned to the well unharmed.[33] In June 2016, a 3.5 ft Alligator Gar was caught from Subhash Sarovar Lake in Kolkata.[34] Other incidents over the years have been random, ranging anywhere from captures in coastal waters during environmental assessments[35] to captures in private ponds.

Human utilization

Early history

Native Americans in the south, and Caribbean peoples used the alligator gar's ganoid scales for arrow heads, breastplates, and as shielding to cover plows. Early settlers tanned the skins to make a strong, durable leather to cover their wooden plows, make purses, and various other items. Gar oil was also used by the people of Arkansas as a repellent for buffalo-gnats.[20]

For nearly half a century, alligator gar were considered "trash fish",[1] or a "nuisance species" by state and federal authorities who targeted them for elimination to protect game fish populations,[3] and to prevent alleged attacks on humans, a claim that remains unsubstantiated with the exception of occasional injuries sustained from captured alligator gar thrashing around on the decks of boats.[18] Fishermen participated in the slaughter of thousands of alligator gar believing they were providing a great service. In 1995, KUHT channel 8, a member PBS television station located on the campus of the University of Houston in Texas, distributed and broadcast the first video documentary ever produced on alligator gar. The documentary, "Alligator Gar:Predator or Prey?", debuted nationally in prime time during the July Sweeps, and according to the Nielsen rating report provided to KUHT, was the number one rated program of the evening.[18] The documentary focused on the physiology and life cycle of alligator gar, addressed the destruction of habitat, the unregulated culling and over harvesting of alligator gar from various lakes in Texas and Louisiana, and expressed concerns for the future of the species at a time when they were still considered a "trash fish".[18] A decade passed before any significant action was taken to protect and preserve the remaining populations of alligator gar in the United States. The Missouri Department of Conservation has since partnered with Tennessee, Arkansas, Kentucky, Illinois, Alabama, Mississippi, Texas, Oklahoma, and Louisiana in restoration and management activities.[20]

Alligator gar ganoid scale jewelry.jpg Earrings from the ganoid scales of alligator gar.jpg AlligatorGarHarvest.jpg Filleting an alligator gar.jpg AlligatorGarPrice.jpg Alligator gar fillets on the grill.jpg
Ganoid scale jewelry Ganoid scale earrings 1995 Choke Canyon Harvest On site processing Market display of gar fillets Fillets grilled, and crab boiled

Sport fish

6 ft (1.8 m) 129 lb (59 kg) alligator gar caught by Steve Zeug and Clint Robertson, Brazos River, Texas, 2004

The long time public perception of alligator gar as "trash fish", or a "nuisance species" has changed with increasing national and international attention on the species as a sport fish which some have attributed to features on popular television shows. Oklahoma, Texas, Arkansas, Mississippi, and Louisiana allow regulated sport fishing of alligator gar. Texas has one of the best remaining fisheries for alligator gar, and in concert with its efforts to maintain a viable fishery, imposed a one-per-day bag limit on them in 2009.[36] The Texas state record, and world record for the largest alligator gar caught on rod and reel is 279 lb (127 kg), taken by Bill Valverde on January 1, 1951 on the Rio Grande in Texas.[37] Alligator gar are also quite popular among bowfishers because of their large size, trophy potential, and fighting ability. The Texas state bowfishing record was set In 2001 by Marty McClellan with a 290 pounds (130 kg) alligator gar from the Trinity River. The all-tackle record was a 302 pounds (137 kg) alligator gar caught on a trotline in 1953 by T.C. Pierce, Jr. In 1991, fishing guide Kirk Kirkland anecdotally reported catching an alligator gar measuring 9 feet 6 inches (2.90 m) on rod and line from the Trinity River.[38]

Commercialization and aquaculture

Declining populations of alligator gar throughout their historic range has resulted in the need to monitor wild populations and regulate commercial harvests. Alligator gar have a high yield of white meat fillets and a small percentage of waste relative to body weight. The meat is sold to wholesale distributors, and also sold retail by a few supermarkets with prices starting at around $3.00/lb. Fried gar balls, grilled fillets, and fillets boiled in water with crab boil seasoning are popular dishes in the south. There is also a small cottage industry that makes jewelry out of ganoid scales, and tans gar hides to produce leather for making lamp shades, purses, and a host of novelty items.[18][20]

Atractosteus gars, including alligator gar, tropical gars, and Cuban gars are considered good candidates for aquaculture particularly in developing regions where their rapid growth, disease resistance, easy adaptation to artificial feeds as juveniles, and ability to tolerate low water quality are essential. Their ability to breathe in both air and water eliminates the need for costly aeration systems and other technology commonly used in aquaculture. In the Southern United States, as well as in parts of Mexico and Cuba, broodstocks have already been established, and are being maintained in their respective regions where they already are a popular food fish.[39]

Aquaria

Alligator gar maneuvering with pectoral fins in large zoo aquarium

Despite the large size alligator gar can attain, they are kept as aquarium fish, though many fish labeled as "alligator gar" in the aquarium trade are actually smaller species. Alligator gar require a very large aquarium or pond, and ample resources in order for them to thrive in captivity. They are also a popular fish for public aquaria, and zoos. It is illegal in many areas to keep alligator gar as pets, but they will occasionally show up in fish stores. Alligator gar are highly prized and sought after for private aquaria, particularly in Japan. According to some reports, large alligator gar could fetch as much as US$40,000 in what some consider the "Japanese black market".[40] In June 2011, three men from Florida and Louisiana were indicted on charges of illegally removing wild alligator gar from the Trinity River in Texas, and attempting to ship them to Japan for private collectors. The indictments resulted from an undercover sting operation by special agents with the U.S. Fish & Wildlife Service, the Texas Parks and Wildlife Department, and the Florida Fish and Wildlife Conservation Commission.[41] The charges included violations of three separate provisions of the Lacey Act, specifically conspiracy to submit a false label for fish transported in interstate commerce; conspiracy to transport fish in interstate commerce in violation of state law or regulation; and conspiracy to transport and sell fish in interstate commerce in violation of state law or regulation.[42] Two of the conspirators entered guilty pleas to one count, and the government dropped the other two charges against them. A third conspirator went to trial on all three counts, was acquitted on one count, and found guilty on two. The district court sentenced him to serve nine months in prison followed by one year of supervised release.[43] The case was appealed, and on April 15, 2014, the appellate court affirmed the judgment of the district court.[44]

References

  1. ^ a b Brady, Tony (August 2013). "Fleur De Lis Fisheries" (PDF). US Fish & Wildlife Service. p. 2. 
  2. ^ Milbrath, Lester W. (1989). Envisioning a Sustainable Society: Learning Our Way Out. SUNY Press. p. 271. ISBN 9780791401620. 
  3. ^ a b Echevarria, Carlos (February 5, 2013). "Alligator Gar, Atractosteus spatula". Warm Springs National Fish Hatchery. US Fish & Wildlife Service. Retrieved July 7, 2014. 
  4. ^ Lochmann, S.E.; Baker, Brandon W.; Rachels, Kyle T.; Timmons, Brett A. "New Research". Aquaculture and Fisheries Center. University of Arkansas at Pine Bluff. Retrieved June 18, 2014. 
  5. ^ a b c d e Goddard, Nathaniel. "Alligator Gar". FLMNH Ichthyology Department. Retrieved April 19, 2014. 
  6. ^ "Alligator Gar (Atractosteus spatula)". Texas Parks & Wildlife Department. Retrieved March 8, 2016. 
  7. ^ "Vicksburg Man Catches 327 Lb. Alligator Gar". WAPT News. February 18, 2011. 
  8. ^ Love, Chad (February 23, 2011). "World Record Alligator Gar Pulled From Mississippi Lake Tangled in Fisherman's Net". Field & Stream. Retrieved April 19, 2014. 
  9. ^ Tyus, Harold M. (2011). Ecology and Conservation of Fishes. CRC Press. p. 46. ISBN 9781439858547. 
  10. ^ "Biology of Fishes-Fish/Biol 311" (PDF). Swimbladder. University of Washington. Retrieved August 2, 2014. 
  11. ^ Perkins, Sid (September 23, 2015). "How The Enamel That Coats Your Teeth Evolved". AAAS. Retrieved January 6, 2017. 
  12. ^ "Tooth Enamel May Have Evolved From Ancient Fish Scales". ABC Science. September 24, 2015. Retrieved January 6, 2017. 
  13. ^ Sherman, Vincent R.; Yaraghi, Nicholas A.; Kisailus, David; Meyers, Marc A. (2016-12-01). "Microstructural and geometric influences in the protective scales of Atractosteus spatula". Journal of The Royal Society Interface. 13 (125): 20160595. doi:10.1098/rsif.2016.0595. ISSN 1742-5689. PMID 27974575. 
  14. ^ Schwartz, Daniel E.; Allen, Peter J. (December 2013). "Comparative biochemistry and physiology. Part A, Molecular and integrative physiology". Mississippi State University Dept. of Wildlife, Fisheries and Aquaculture. 
  15. ^ "The American Naturalist". 35. University of Chicago Press. JSTOR 2453768. 
  16. ^ Warren, Melvin L. Jr.; Burr, Brooks M. Freshwater Fishes of North America. 1. Johns Hopkins University Press. p. 250. ISBN 1421412012. 
  17. ^ Mayor, Adrienne (2005). Fossil Legends of the First Americans. Princeton University Press. p. 38. ISBN 9781400849314. 
  18. ^ a b c d e f g h "Alligator Gar (Atractosteus spatula)". 2011. Retrieved January 6, 2017. 
  19. ^ Graham, Jeffrey B. (1997). Air-Breathing Fishes: Evolution, Diversity, and Adaptation. Academic Press. pp. 1–10. ISBN 0-12-294860-2. 
  20. ^ a b c d "Missouri Alligator Gar Management and Restoration Plan" (PDF). Missouri Department of Conservation Fisheries Division. January 22, 2013. Retrieved August 1, 2016. 
  21. ^ Buckmeier, David L. (July 31, 2008). "Life History and Status of Alligator Gar (Atractosteus spatula), with Recommendations for Management" (PDF). Heart of Hills Fisheries Science Center. Texas Parks and Wildlife Department. p. 5. Retrieved July 7, 2014. 
  22. ^ a b "BBest Recommendations Report" (PDF). Sabine/Neches BBest Biological Overlay Approach. Best Biological Subcommittee, Texas Commission on Environmental Quality, U.S. November 2, 2009. p. 8. Retrieved July 7, 2014. 
  23. ^ a b Thompkins, Shannon (April 19, 2014). "Once a nuisance, alligator gar increasingly protected". Houston Chronicle. 
  24. ^ "Alligator Gar Technical Committee". Southern Division of the American Fisheries Society. Retrieved May 17, 2013. 
  25. ^ Poly, William J. (2001). "Distribution of the Alligator Gar, Atractosteus spatula (Lacépède, 1803), in Illinois" (PDF). Transactions of the Illinois State Academy of Science. 94 (3): 185–190. 
  26. ^ Webber, Tammy (July 29, 2016). "Huge, once-hated fish now seen as weapon against Asian carp". Pantagraph. Associated Press. Retrieved July 31, 2016. 
  27. ^ "Hazar deňziniň türkmen kenarynda amerikan sowutly çortanyň tutulmagynyň ilkinji wakasy" (in Turkmen). Türkmenistanyň Tebigaty goramak ministrligi. Retrieved May 18, 2015. 
  28. ^ Salnikov, V. B. (April 2011). "Russian Journal of Biological Invasions". Erratum to: "First Finding of Gar Atractosteus sp. (Actinopterygii, Lepisosteiformes, Lepisosteidae) in the Caspian Sea near the Coast of Turkmenistan". Springer. 2 (2): 240. doi:10.1134/S2075111711030118. 
  29. ^ "Monster Exotic Fish Found In Hong Kong Ponds". ABS-CBN News. September 5, 2009. Retrieved July 4, 2016. 
  30. ^ Nip, Amy (January 10, 2010). "Feared in public ponds, admired behind glass". South China Morning Post. 
  31. ^ Spitzer, Mark. "When Gars Attack". Southeast Missouri State University. Retrieved July 4, 2016. 
  32. ^ "Friends Catch 1.5m 'Monster' Fish From Pasir Ris Canal After Long Struggle". The Straits Times. January 21, 2011. 
  33. ^ Singh, Vijay (August 6, 2015). "Exotic Alligator Gar fish rescued in Dadar". The Times of India. Bennett, Coleman & Co. Ltd. Retrieved December 6, 2015. 
  34. ^ Kolkata: Discovery of predator fish that resembles an alligator concerns experts. Hindustan Times (June 22, 2016). Retrieved on 2016-11-10.
  35. ^ Kumaraguru, A.K.; Kannan, R. and Sundaramahalingam, A. (March 2000). "Studies on Socioeconomics of Coral Reef Resource Users in the Gulf of Mannar Coast, South India" (PDF). Planning Commission Project. Centre for Marine and Coastal Studies. Retrieved December 6, 2015.  CS1 maint: Uses authors parameter (link)
  36. ^ "Alligator Gar". Texas Parks and Wildlife Department. Retrieved April 21, 2014. 
  37. ^ "State Freshwater Records: Rod and Reel". Texas Parks & Wildlife. Retrieved May 17, 2013. 
  38. ^ "Big Fish Stories Can Have Happier Endings". Texas Parks & Wildlife. May 16, 2011. 
  39. ^ Alfaro, Roberto M.; Gonzales, Carlos A.; Ferrara, Allyse (2008). "Gar biology and culture: status and prospects" (PDF). Chapter 39. Aquaculture Research. pp. 748–763. Retrieved July 7, 2014. 
  40. ^ Horswell, Cindy (June 17, 2011). "Indictments accuse 3 of taking alligator gar fish out of Trinity". Houston Chronicle. 
  41. ^ Berstein, Jon (October 15, 2011). "Monster fish tale: Alligator gar sting ends in conviction". SunSentinel. 
  42. ^ "Accused alligator gar smugglers busted in trinity river operation". ABC 9 KTRE. 2011. 
  43. ^ "United States v. Loren Willis et al., Nos. 9:11-CR-00028, 1:11-CR-20676 (E.D. Tex., S.D. Fla.), AUSAs Reynaldo Morin and Jaime Raiche" (PDF). Monthly Bulletin. Regional EnvironmentalEnforcement Association. October 2012. Retrieved July 4, 2016. 
  44. ^ "Opinions" (PDF). U.S. Court of Appeals. April 15, 2014. 

Further reading

External links

source: http://en.wikipedia.org/wiki/Alligator_gar

Insect Art

There are apparently lots of creative things to do with insects

insect lab art, grasshopper

Insect lab art, beetle

Insect Lab produces chimeras of insects and machinery, a beautiful juxtaposition of nature and technology and a singular, handcrafted piece of insect art.


 

Damien Hirst’s butterfly artwork  http://www.damienhirst.com/


Steven Kutcher composes (live) insects of all kinds in an interesting kinesthetic insect art http://www.bugartbysteven.com/


 

Edouard Martinet converts scrap metal and found treasures into works of insect art.

 


Duprat's aquatic caddis fly larvae, Photos Jean-Luc Fournier. From http://www.cabinetmagazine.org/issues/25/duprat.php

This work is the results of Hubert Duprat’s novel use of caddis fly larvae and their interesting habits. These critters protect themselves by manufacturing their own body-sheath from what would normally be found near streams and ponds…so sand, dirt, leaves and such spun together with the insect’s silk. These remarkable insects aren’t remarkable because the discriminate between dirt and gold. From http://www.cabinetmagazine.org.  Please watch a short film of this in action.

Nature Impressions: Riusuke Fukahori’s genius

This is easily the best thing I’ve found for this blog series so far.  This is why in my opinion:

1. It deals with fish (big plus in my book)

2. It is a novel medium (to me at least)

3. It is a beautiful balance of art and nature (prerequisite for sharing).

 

 

Fukahori’s work is a mind bending expression that attempts to capture nature’s unique moments.  What I see in this art is reminiscent of what one might experience when gazing into a stream along its bank, everything frozen in time.  He has mastered painting images into 3D blocks of resin, painting a layer, adding resin, painting a layer, adding resin, and so on.  The effect is stunningly realistic scenes of fish swimming in schools in small containers. Most of his paintings are of goldfish or carp. See our Asian Carp gyotaku, Common Carp, for an alternate version of an artistic impression of this fish. The artist’s website is here.

Images from Dominic’s pics on Flickr

Here’s a video of him in action; enjoy

Blacktip Shark 3

 

Blacktip Shark Gyotaku #3 by Inked Animal

Blacktip Shark | Carcharhinus limbatus


Blacktip Shark info via Wikipedia:

Not to be confused with the blacktip reef shark, Carcharhinus melanopterus.
Blacktip shark
Carcharhinus limbatus (2).jpg
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Superorder: Selachimorpha
Order: Carcharhiniformes
Family: Carcharhinidae
Genus: Carcharhinus
Species: C. limbatus
Binomial name
Carcharhinus limbatus
(J. P. Müller & Henle, 1839)
Carcharhinus limbatus distmap.png
Range of the blacktip shark
Synonyms

Carcharias abbreviatus Klunzinger, 1871
Carcharias aethalorus Jordan & Gilbert, 1882
Carcharias ehrenbergi Klunzinger, 1871
Carcharias maculipinna Günther, 1868
Carcharias microps Lowe, 1841
Carcharias muelleri Steindachner, 1867
Carcharias phorcys Jordan & Evermann, 1903
Carcharias pleurotaenia Bleeker, 1852
Carcharhinus natator Meek & Hildebrand, 1923

The blacktip shark (Carcharhinus limbatus) is a species of requiem shark, and part of the family Carcharhinidae. It is common to coastal tropical and subtropical waters around the world, including brackish habitats. Genetic analyses have revealed substantial variation within this species, with populations from the western Atlantic Ocean isolated and distinct from those in the rest of its range. The blacktip shark has a stout, fusiform body with a pointed snout, long gill slits, and no ridge between the dorsal fins. Most individuals have black tips or edges on the pectoral, dorsal, pelvic, and caudal fins. It usually attains a length of 1.5 m (4.9 ft).

Swift, energetic piscivores, blacktip sharks are known to make spinning leaps out of the water while attacking schools of small fish. Their demeanor has been described as "timid" compared to other large requiem sharks. Both juveniles and adults form groups of varying size. Like other members of its family, the blacktip shark is viviparous; females bear one to 10 pups every other year. Young blacktip sharks spend the first months of their lives in shallow nurseries, and grown females return to the nurseries where they were born to give birth themselves. In the absence of males, females are also capable of asexual reproduction.

Normally wary of humans, blacktip sharks can become aggressive in the presence of food and have been responsible for a number of attacks on people. This species is of importance to both commercial and recreational fisheries across many parts of its range, with its meat, skin, fins, and liver oil used. It has been assessed as Near Threatened by the IUCN, on the basis of its low reproductive rate and high value to fishers.

Taxonomy

The blacktip shark was first described by French zoologist Achille Valenciennes as Carcharias (Prionodon) limbatus in Johannes Müller and Friedrich Henle's 1839 Systematische Beschreibung der Plagiostomen. The type specimens were two individuals caught off Martinique, both of which have since been lost. Later authors moved this species to the genus Carcharhinus.[1][2] The specific epithet limbatus is Latin for "bordered", referring to the black edges of this shark's fins.[3] Other common names used for the blacktip shark include blackfin shark, blacktip whaler, common or small blacktip shark, grey shark, and spotfin ground shark.[4]

Phylogeny and evolution

The closest relatives of the blacktip shark were originally thought to be the graceful shark (C. amblyrhynchoides) and the spinner shark (C. brevipinna), due to similarities in morphology and behavior. However, this interpretation has not been borne out by studies of mitochondrial and ribosomal DNA, which instead suggest affinity with the blacknose shark (C. acronotus). More work is required to fully resolve the relationship between the blacktip shark and other Carcharhinus species.[5]

Analysis of mitochondrial DNA has also revealed two distinct lineages within this species, one occupying the western Atlantic and the other occupying the eastern Atlantic, Indian, and Pacific Oceans. This suggests that Indo-Pacific blacktip sharks are descended from those in the eastern Atlantic, while the western Atlantic sharks became isolated by the widening Atlantic Ocean on one side and the formation of the Isthmus of Panama on the other. Blacktip sharks from these two regions differ in morphology, coloration, and life history characteristics, and the eastern Atlantic lineage may merit species status.[6] Fossil teeth belonging to this species have been found in Early Miocene (23–16 Ma) deposits in Delaware and Florida.[7][8]

Description

The blacktip shark has a robust, streamlined body with a long, pointed snout and relatively small eyes. The five pairs of gill slits are longer than those of similar requiem shark species.[1] The jaws contain 15 tooth rows on either side, with two symphysial teeth (at the jaw midline) in the upper jaw and one symphysial tooth in the lower jaw. The teeth are broad-based with a high, narrow cusp and serrated edges.[2] The first dorsal fin is tall and falcate (sickle-shaped) with a short free rear tip; no ridge runs between the first and second dorsal fins. The large pectoral fins are falcate and pointed.[1]

The coloration is gray to brown above and white below, with a conspicuous white stripe running along the sides. The pectoral fins, second dorsal fin, and the lower lobe of the caudal fin usually have black tips. The pelvic fins and rarely the anal fin may also be black-tipped. The first dorsal fin and the upper lobe of the caudal fin typically have black edges.[1] Some larger individuals have unmarked or nearly unmarked fins.[3] Blacktip sharks can temporarily lose almost all their colors during blooms, or "whitings", of coccolithophores.[9] This species attains a maximum known length of 2.8 m (9.2 ft), though 1.5 m (4.9 ft) is more typical, and a maximum known weight of 123 kg (271 lb).[4]

Distribution and habitat

A blacktip shark swimming in murky water off Oahu, Hawaii

The blacktip shark has a worldwide distribution in tropical and subtropical waters. In the Atlantic, it is found from Massachusetts to Brazil, including the Gulf of Mexico and the Caribbean Sea, and from the Mediterranean Sea, Madeira, and the Canary Islands to the Democratic Republic of the Congo. It occurs all around the periphery of the Indian Ocean, from South Africa and Madagascar to the Arabian Peninsula and the Indian subcontinent, to Southeast Asia. In the western Pacific, it is found from southern China to northern Australia, including the Philippines and Indonesia. In the eastern Pacific, it occurs from Baja California to Peru. It has also been reported at a number of Pacific islands, including New Caledonia, Tahiti, the Marquesas, Hawaii, Revillagigedo, and the Galápagos.[1]

Most blacktip sharks are found in water less than 30 m (98 ft) deep over continental and insular shelves, though they may dive to 64 m (210 ft).[4] Favored habitats are muddy bays, island lagoons, and the drop-offs near coral reefs; they are also tolerant of low salinity and enter estuaries and mangrove swamps. Although an individual may be found some distance offshore, blacktip sharks do not inhabit oceanic waters.[1] Seasonal migration has been documented for the population off the east coast of the United States, moving north to North Carolina in the summer and south to Florida in the winter.[10]

Biology and ecology

The blacktip shark is an extremely fast, energetic predator that is usually found in groups of varying size.[3] Segregation by sex and age does not occur; adult males and nonpregnant females are found apart from pregnant females, and both are separated from juveniles.[1] In Terra Ceia Bay, Florida, a nursery area for this species, juvenile blacktips form aggregations during the day and disperse at night. They aggregate most strongly in the early summer when the sharks are youngest, suggesting that they are seeking refuge from predators (mostly larger sharks) in numbers.[11] Predator avoidance may also be the reason why juvenile blacktips do not congregate in the areas of highest prey density in the bay.[12] Adults have no known predators.[2] Known parasites of the blacktip shark include the copepods Pandarus sinuatus and P. smithii, and the monogeneans Dermophthirius penneri and Dionchus spp., which attach the shark's skin.[2][13][14] This species is also parasitized by nematodes in the family Philometridae, which infest the ovaries.[15]

Behaviour

Blacktip sharks are social and usually found in groups.

Like the spinner shark, the blacktip shark is known to leap out of the water and spin three or four times about its axis before landing. Some of these jumps are the end product of feeding runs, in which the shark corkscrews vertically through schools of small fish and its momentum launches it into the air.[3] Observations in the Bahamas suggest that blacktip sharks may also jump out of the water to dislodge attached sharksuckers (Echeneis naucrates), which irritate the shark's skin and compromise its hydrodynamic shape.[16] The speed attained by the shark during these jumps has been estimated to average 6.3 m/s (21 ft/s).[17]

Blacktip sharks have a timid disposition and consistently lose out to Galapagos sharks (C. galapagensis) and silvertip sharks (C. albimarginatus) of equal size when competing for food.[1] If threatened or challenged, they may perform an agonistic display: the shark swims towards the threat and then turns away, while rolling from side to side, lowering its pectoral fins, tilting its head and tail upwards, and making sideways biting motions. The entire sequence lasts around 25 seconds. This behavior is similar to the actions of a shark attempting to move a sharksucker; one of these behaviors possibly is derived from the other.[18]

Feeding

Fish make up some 90% of the blacktip shark's diet.[19] A wide variety of fish have been recorded as prey for this species: sardines, herring, anchovies, ladyfish, sea catfish, cornetfish, flatfish, threadfins, mullet, mackerel, jacks, groupers, snook, porgies, mojarras, emperors, grunts, butterfish, tilapia, triggerfish, boxfish, and porcupinefish. They also feed on rays and skates, as well as smaller sharks such as smoothhounds and sharpnose sharks. Crustaceans and cephalopods are occasionally taken.[1] In the Gulf of Mexico, the most important prey of the blacktip shark is the Gulf menhaden (Brevoortia patronus), followed by the Atlantic croaker (Micropogonias undulatus).[19] Off South Africa, jacks and herring are the most important prey.[20] Hunting peaks at dawn and dusk.[19] The excitability and sociability of blacktip sharks makes them prone to feeding frenzies when large quantities of food are suddenly available, such as when fishing vessels dump their refuse overboard.[1]

Life history

As with other requiem sharks, the blacktip shark exhibits vivipary. Females typically give birth to four to seven (range one to 10) pups every other year, making use of shallow coastal nurseries that offer plentiful food and fewer predators.[1] Known nurseries include Pine Island Sound, Terra Ceia Bay, and Yankeetown along the Gulf Coast of Florida, Bulls Bay on the coast of South Carolina, and Pontal do Paraná on the coast of Brazil.[21][22] Although adult blacktip sharks are highly mobile and disperse over long distances, they are philopatric and return to their original nursery areas to give birth. This results in a series of genetically distinct breeding stocks that overlap in geographic range.[21][23]

Mating occurs from spring to early summer, and the young are born around the same time the following year after a gestation period of 10–12 months.[1] Females have one functional ovary and two functional uteri; each uterus is separated into compartments with a single embryo inside each.[24] The embryos are initially sustained by a yolk sac; in the 10th or 11th week of gestation, when the embryo measures 18–19 cm long (7.1–7.5 in), the supply of yolk is exhausted and the yolk sac develops into a placental connection that sustains the embryo until birth.[10] The length at birth is 55–60 cm (22–24 in) off the eastern United States and 61–65 cm (24–26 in) off North Africa.[10][24] The mortality rate in the first 15 months of life is 61–91%, with major threats being predation and starvation.[25] The young remain in the nurseries until their first fall, when they migrate to their wintering grounds.[10]

The growth rate of this species slows with age: 25–30 cm (9.8–11.8 in) in the first six months, then 20 cm (7.9 in) a year until the second year, then 10 cm (3.9 in) a year until maturation, then 5 cm (2.0 in) a year for adults.[26][27] The size at maturity varies geographically: males and females mature at 1.4–1.5 m (4.6–4.9 ft) and 1.6 m (5.2 ft), respectively, in the northeastern Atlantic,[10] 1.3–1.4 m (4.3–4.6 ft) and 1.5–1.6 m (4.9–5.2 ft), respectively, in the Gulf of Mexico,[26][28] 1.5 and 1.6 m (4.9 and 5.2 ft) respectively off South Africa,[29] and 1.7 and 1.8 m (5.6 and 5.9 ft), respectively, off North Africa.[24] The age at maturation is 4–5 years for males and 7–8 years for females.[26][28] The lifespan is at least 12 years.[1]

In 2007, a 9-year-old female blacktip shark at the Virginia Aquarium and Marine Science Center was found to be pregnant with a single near-term female pup, despite having never mated with a male. Genetic analysis confirmed that her offspring was the product of automictic parthenogenesis, a form of asexual reproduction in which an ovum merges with a polar body to form a zygote without fertilization. Along with an earlier case of parthenogenesis in the bonnethead (Sphyrna tiburo), this event suggests that asexual reproduction may be more widespread in sharks than previously thought.[30]

Human interactions

The blacktip shark usually poses little danger to divers.

Blacktip sharks showing curiosity towards divers has been reported, but they remain at a safe distance. Under most circumstances, these timid sharks are not regarded as highly dangerous to humans. However, they may become aggressive in the presence of food, and their size and speed invite respect.[1] As of 2008, the International Shark Attack File lists 28 unprovoked attacks (one fatal) and 13 provoked attacks by this species.[31] Blacktip sharks are responsible annually for 16% of the shark attacks around Florida. Most attacks by this species result in only minor wounds.[2]

As one of the most common large sharks in coastal waters, the blacktip shark is caught in large numbers by commercial fisheries throughout the world, using longlines, fixed-bottom nets, bottom trawls, and hook-and-line. The meat is of high quality and marketed fresh, frozen, or dried and salted. In addition, the fins are used for shark fin soup, the skin for leather, the liver oil for vitamins, and the carcasses for fishmeal.[1] Blacktip sharks are one of the most important species to the northwestern Atlantic shark fishery, second only to the sandbar shark (C. plumbeus). The flesh is considered superior to that of the sandbar shark, resulting in the sandbar and other requiem shark species being sold under the name "blacktip shark" in the United States. The blacktip shark is also very significant to Indian and Mexican fisheries, and is caught in varying numbers by fisheries in the Mediterranean and South China Seas, and off northern Australia.[27]

The blacktip shark is popular with recreational anglers in Florida, the Caribbean, and South Africa. It is listed as a game fish by the International Game Fish Association. Once hooked, this species is a strong, steady fighter that sometimes jumps out of the water.[2] Since 1995, the number of blacktip sharks taken by recreational anglers in the United States has approached or surpassed the number taken by commercial fishing.[27] The International Union for Conservation of Nature has assessed the blacktip shark as Near Threatened, as its low reproductive rate renders it vulnerable to overfishing.[32] The United States and Australia are the only two countries that manage fisheries catching blacktip sharks. In both cases, regulation occurs under umbrella management schemes for multiple shark species, such as that for the large coastal sharks category of the US National Marine Fisheries Service Atlantic shark Fisheries Management Plan. No conservation plans specifically for this species have been implemented.[27]

References

  1. ^ a b c d e f g h i j k l m n o Compagno, L.J.V. (1984). Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date. Rome: Food and Agricultural Organization. pp. 481–483. ISBN 92-5-101384-5. 
  2. ^ a b c d e f Curtis, T. Biological Profiles: Blacktip Shark. Florida Museum of Natural History Ichthyology Department. Retrieved on April 27, 2009.
  3. ^ a b c d Ebert, D.A. (2003). Sharks, Rays, and Chimaeras of California. London: University of California Press. pp. 156–157. ISBN 0-520-23484-7. 
  4. ^ a b c Froese, Rainer and Pauly, Daniel, eds. (2009). "Carcharhinus limbatus" in FishBase. April 2009 version.
  5. ^ Dosay-Akbulut, M. (2008). "The phylogenetic relationship within the genus Carcharhinus". Comptes Rendus Biologies. 331 (7): 500–509. doi:10.1016/j.crvi.2008.04.001. PMID 18558373. 
  6. ^ Keeney, D.B. & Heist, E.J. (October 2006). "Worldwide phylogeography of the blacktip shark (Carcharhinus limbatus) inferred from mitochondrial DNA reveals isolation of western Atlantic populations coupled with recent Pacific dispersal". Molecular Ecology. 15 (12): 3669–3679. doi:10.1111/j.1365-294X.2006.03036.x. PMID 17032265. 
  7. ^ Benson. R.N., ed. (1998). Geology and Paleontology of the Lower Miocene Pollack Farm Fossil Site, Delaware: Delaware Geological Survey Special Publication No. 21. Delaware Natural History Survey. pp. 133–139. 
  8. ^ Brown, R.C. (2008). Florida's Fossils: Guide to Location, Identification, and Enjoyment (third ed.). Pineapple Press Inc. p. 100. ISBN 1-56164-409-9. 
  9. ^ Martin, R.A. Albinism in Sharks. ReefQuest Centre for Shark Research. Retrieved on April 28, 2009.
  10. ^ a b c d e Castro, J.I. (November 1996). "Biology of the blacktip shark, Carcharhinus limbatus, off the southeastern United States". Bulletin of Marine Science. 59 (3): 508–522. 
  11. ^ Heupel, M.R. & Simpfendorfer, C.A. (2005). "Quantitative analysis of aggregation behavior in juvenile blacktip sharks". Marine Biology. 147 (5): 1239–1249. doi:10.1007/s00227-005-0004-7. 
  12. ^ Heupel, M.R. & Hueter, R.E. (2002). "The importance of prey density in relation to the movement patterns of juvenile sharks within a coastal nursery area". Marine and Freshwater Research. 53 (2): 543–550. doi:10.1071/MF01132. 
  13. ^ Bullard, S.A.; Frasca, A. (Jr.) & Benz, G.W. (June 2000). "Skin Lesions Caused by Dermophthirius penneri (Monogenea: Microbothriidae) on Wild-Caught Blacktip Sharks (Carcharhinus limbatus)". Journal of Parasitology. 86 (3): 618–622. doi:10.1645/0022-3395(2000)086[0618:SLCBDP]2.0.CO;2. PMID 10864264.  CS1 maint: Date and year (link)
  14. ^ Bullard, S.A.; Benz, G.W. & Braswell, J.S. (2000). "Dionchus postoncomiracidia (Monogenea: Dionchidae) from the skin of blacktip sharks, Carcharhinus limbatus (Carcharhinidae)". Journal of Parasitology. 86 (2): 245–250. doi:10.1645/0022-3395(2000)086[0245:DPMDFT]2.0.CO;2. JSTOR 3284763. PMID 10780540. 
  15. ^ Rosa-Molinar, E. & Williams, C.S. (1983). "Larval nematodes (Philometridae) in granulomas in ovaries of blacktip sharks, Carcharhinus limbatus (Valenciennes)". Journal of Wildlife Diseases. 19 (3): 275–277. doi:10.7589/0090-3558-19.3.275. PMID 6644926. 
  16. ^ Riner, E.K. & Brijnnschweiler, J.M. (2003). "Do sharksuckers, Echeneis naucrates, induce jump behaviour in blacktip sharks, Carcharhinus limbatus?". Marine and Freshwater Behaviour and Physiology. 36 (2): 111–113. doi:10.1080/1023624031000119584. 
  17. ^ Brunnschweiler, J.M. (2005). "Water-escape velocities in jumping blacktip sharks". Journal of the Royal Society Interface. 2 (4): 389–391. doi:10.1098/rsif.2005.0047. PMC 1578268Freely accessible. PMID 16849197. 
  18. ^ Ritter, E.K. & Godknecht, A.J. (February 1, 2000). Ross, S. T., ed. "Agonistic Displays in the Blacktip Shark (Carcharhinus limbatus)". Copeia. 2000 (1): 282–284. doi:10.1643/0045-8511(2000)2000[0282:ADITBS]2.0.CO;2. JSTOR 1448264.  CS1 maint: Date and year (link)
  19. ^ a b c Barry, K.P. (2002). Feeding habits of blacktip sharks, Carcharhinus limbatus, and Atlantic sharpnose sharks, Rhizoprionodon terraenovae, in Louisiana coastal waters. MS thesis, Louisiana State University, Baton Rouge.
  20. ^ Dudley, S.F.J. & Cliff, G. (1993). "Sharks caught in the protective gill nets off Natal, South Africa. 7. The blacktip shark Carcharhinus limbatus (Valenciennes)". African Journal of Marine Science. 13: 237–254. doi:10.2989/025776193784287356. 
  21. ^ a b Keeney, D.B.; Heupel, M.; Hueter, R.E. & Heist, E.J. (2003). "Genetic heterogeneity among blacktip shark, Carcharhinus limbatus, continental nurseries along the U.S. Atlantic and Gulf of Mexico". Marine Biology. 143 (6): 1039–1046. doi:10.1007/s00227-003-1166-9. 
  22. ^ Bornatowski, H. (2008). "A parturition and nursery area for Carcharhinus limbatus (Elasmobranchii, Carcharhinidae) off the coast of Paraná, Brazil". Brazilian Journal of Oceanography. 56 (4): 317–319. doi:10.1590/s1679-87592008000400008. 
  23. ^ Keeney, D.B.; Heupel, M.R.; Hueter, R.E. & Heist, E.J. (2005). "Microsatellite and mitochondrial DNA analyses of the genetic structure of blacktip shark (Carcharhinus limbatus) nurseries in the northwestern Atlantic, Gulf of Mexico, and Caribbean Sea". Molecular Ecology. 14 (7): 1911–1923. doi:10.1111/j.1365-294X.2005.02549.x. PMID 15910315. 
  24. ^ a b c Capapé, C.H.; Seck, A.A.; Diatta, Y.; Reynaud, C.H.; Hemida, F. & Zaouali, J. (2004). "Reproductive biology of the blacktip shark, Carcharhinus limbatus (Chondrichthyes: Carcharhinidae) off West and North African Coasts" (PDF). Cybium. 28 (4): 275–284. 
  25. ^ Heupel, M.R. & Simpfendorfer, C.A. (2002). "Estimation of mortality of juvenile blacktip sharks, Carcharhinus limbatus, within a nursery area using telemetry data". Canadian Journal of Fisheries and Aquatic Sciences. 59 (4): 624–632. doi:10.1139/f02-036. 
  26. ^ a b c Branstetter, S. (December 9, 1987). "Age and Growth Estimates for Blacktip, Carcharhinus limbatus, and Spinner, C. brevipinna, Sharks from the Northwestern Gulf of Mexico". Copeia. American Society of Ichthyologists and Herpetologists. 1987 (4): 964–974. doi:10.2307/1445560. JSTOR 1445560. 
  27. ^ a b c d Fowler, S.L.; Cavanagh, R.D.; Camhi, M.; Burgess, G.H.; Cailliet, G.M.; Fordham, S.V.; Simpfendorfer, C.A. & Musick, J.A. (2005). Sharks, Rays and Chimaeras: The Status of the Chondrichthyan Fishes. International Union for Conservation of Nature and Natural Resources. pp. 106–109, 293–295. ISBN 2-8317-0700-5. 
  28. ^ a b Killam, K.A. & Parsons, G.R. (May 1989). "Age and Growth of the Blacktip Shark, Carcharhinus limbatus, near Tampa Bay" (PDF). Florida Fishery Bulletin. 87: 845–857. 
  29. ^ Wintner, S.P. & Cliff, G. (1996). "Age and growth determination of the blacktip shark, Carcharhinus limbatus, from the east coast of South Africa" (PDF). Fishery Bulletin. 94 (1): 135–144. 
  30. ^ Chapman, D.D.; Firchau, B. & Shivji, M.S. (2008). "Parthenogenesis in a large-bodied requiem shark, the blacktip Carcharhinus limbatus". Journal of Fish Biology. 73 (6): 1473–1477. doi:10.1111/j.1095-8649.2008.02018.x. 
  31. ^ ISAF Statistics on Attacking Species of Shark. International Shark Attack File, Florida Museum of Natural History, University of Florida. Retrieved on April 22, 2009.
  32. ^ Musick, J.A.; Fowler, S. (2000). "Carcharhinus limbatus". IUCN Red List of Threatened Species. Version 2007. International Union for Conservation of Nature. Retrieved April 27, 2009. 
source: http://en.wikipedia.org/wiki/Blacktip_shark

Blacktip Shark 2

Blacktip Shark 2 by Inked Animal

Blacktip Shark | Carcharhinus limbatus



Blacktip Shark info via Wikipedia:

Not to be confused with the blacktip reef shark, Carcharhinus melanopterus.
Blacktip shark
Carcharhinus limbatus (2).jpg
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Superorder: Selachimorpha
Order: Carcharhiniformes
Family: Carcharhinidae
Genus: Carcharhinus
Species: C. limbatus
Binomial name
Carcharhinus limbatus
(J. P. Müller & Henle, 1839)
Carcharhinus limbatus distmap.png
Range of the blacktip shark
Synonyms

Carcharias abbreviatus Klunzinger, 1871
Carcharias aethalorus Jordan & Gilbert, 1882
Carcharias ehrenbergi Klunzinger, 1871
Carcharias maculipinna Günther, 1868
Carcharias microps Lowe, 1841
Carcharias muelleri Steindachner, 1867
Carcharias phorcys Jordan & Evermann, 1903
Carcharias pleurotaenia Bleeker, 1852
Carcharhinus natator Meek & Hildebrand, 1923

The blacktip shark (Carcharhinus limbatus) is a species of requiem shark, and part of the family Carcharhinidae. It is common to coastal tropical and subtropical waters around the world, including brackish habitats. Genetic analyses have revealed substantial variation within this species, with populations from the western Atlantic Ocean isolated and distinct from those in the rest of its range. The blacktip shark has a stout, fusiform body with a pointed snout, long gill slits, and no ridge between the dorsal fins. Most individuals have black tips or edges on the pectoral, dorsal, pelvic, and caudal fins. It usually attains a length of 1.5 m (4.9 ft).

Swift, energetic piscivores, blacktip sharks are known to make spinning leaps out of the water while attacking schools of small fish. Their demeanor has been described as "timid" compared to other large requiem sharks. Both juveniles and adults form groups of varying size. Like other members of its family, the blacktip shark is viviparous; females bear one to 10 pups every other year. Young blacktip sharks spend the first months of their lives in shallow nurseries, and grown females return to the nurseries where they were born to give birth themselves. In the absence of males, females are also capable of asexual reproduction.

Normally wary of humans, blacktip sharks can become aggressive in the presence of food and have been responsible for a number of attacks on people. This species is of importance to both commercial and recreational fisheries across many parts of its range, with its meat, skin, fins, and liver oil used. It has been assessed as Near Threatened by the IUCN, on the basis of its low reproductive rate and high value to fishers.

Taxonomy

The blacktip shark was first described by French zoologist Achille Valenciennes as Carcharias (Prionodon) limbatus in Johannes Müller and Friedrich Henle's 1839 Systematische Beschreibung der Plagiostomen. The type specimens were two individuals caught off Martinique, both of which have since been lost. Later authors moved this species to the genus Carcharhinus.[1][2] The specific epithet limbatus is Latin for "bordered", referring to the black edges of this shark's fins.[3] Other common names used for the blacktip shark include blackfin shark, blacktip whaler, common or small blacktip shark, grey shark, and spotfin ground shark.[4]

Phylogeny and evolution

The closest relatives of the blacktip shark were originally thought to be the graceful shark (C. amblyrhynchoides) and the spinner shark (C. brevipinna), due to similarities in morphology and behavior. However, this interpretation has not been borne out by studies of mitochondrial and ribosomal DNA, which instead suggest affinity with the blacknose shark (C. acronotus). More work is required to fully resolve the relationship between the blacktip shark and other Carcharhinus species.[5]

Analysis of mitochondrial DNA has also revealed two distinct lineages within this species, one occupying the western Atlantic and the other occupying the eastern Atlantic, Indian, and Pacific Oceans. This suggests that Indo-Pacific blacktip sharks are descended from those in the eastern Atlantic, while the western Atlantic sharks became isolated by the widening Atlantic Ocean on one side and the formation of the Isthmus of Panama on the other. Blacktip sharks from these two regions differ in morphology, coloration, and life history characteristics, and the eastern Atlantic lineage may merit species status.[6] Fossil teeth belonging to this species have been found in Early Miocene (23–16 Ma) deposits in Delaware and Florida.[7][8]

Description

The blacktip shark has a robust, streamlined body with a long, pointed snout and relatively small eyes. The five pairs of gill slits are longer than those of similar requiem shark species.[1] The jaws contain 15 tooth rows on either side, with two symphysial teeth (at the jaw midline) in the upper jaw and one symphysial tooth in the lower jaw. The teeth are broad-based with a high, narrow cusp and serrated edges.[2] The first dorsal fin is tall and falcate (sickle-shaped) with a short free rear tip; no ridge runs between the first and second dorsal fins. The large pectoral fins are falcate and pointed.[1]

The coloration is gray to brown above and white below, with a conspicuous white stripe running along the sides. The pectoral fins, second dorsal fin, and the lower lobe of the caudal fin usually have black tips. The pelvic fins and rarely the anal fin may also be black-tipped. The first dorsal fin and the upper lobe of the caudal fin typically have black edges.[1] Some larger individuals have unmarked or nearly unmarked fins.[3] Blacktip sharks can temporarily lose almost all their colors during blooms, or "whitings", of coccolithophores.[9] This species attains a maximum known length of 2.8 m (9.2 ft), though 1.5 m (4.9 ft) is more typical, and a maximum known weight of 123 kg (271 lb).[4]

Distribution and habitat

A blacktip shark swimming in murky water off Oahu, Hawaii

The blacktip shark has a worldwide distribution in tropical and subtropical waters. In the Atlantic, it is found from Massachusetts to Brazil, including the Gulf of Mexico and the Caribbean Sea, and from the Mediterranean Sea, Madeira, and the Canary Islands to the Democratic Republic of the Congo. It occurs all around the periphery of the Indian Ocean, from South Africa and Madagascar to the Arabian Peninsula and the Indian subcontinent, to Southeast Asia. In the western Pacific, it is found from southern China to northern Australia, including the Philippines and Indonesia. In the eastern Pacific, it occurs from Baja California to Peru. It has also been reported at a number of Pacific islands, including New Caledonia, Tahiti, the Marquesas, Hawaii, Revillagigedo, and the Galápagos.[1]

Most blacktip sharks are found in water less than 30 m (98 ft) deep over continental and insular shelves, though they may dive to 64 m (210 ft).[4] Favored habitats are muddy bays, island lagoons, and the drop-offs near coral reefs; they are also tolerant of low salinity and enter estuaries and mangrove swamps. Although an individual may be found some distance offshore, blacktip sharks do not inhabit oceanic waters.[1] Seasonal migration has been documented for the population off the east coast of the United States, moving north to North Carolina in the summer and south to Florida in the winter.[10]

Biology and ecology

The blacktip shark is an extremely fast, energetic predator that is usually found in groups of varying size.[3] Segregation by sex and age does not occur; adult males and nonpregnant females are found apart from pregnant females, and both are separated from juveniles.[1] In Terra Ceia Bay, Florida, a nursery area for this species, juvenile blacktips form aggregations during the day and disperse at night. They aggregate most strongly in the early summer when the sharks are youngest, suggesting that they are seeking refuge from predators (mostly larger sharks) in numbers.[11] Predator avoidance may also be the reason why juvenile blacktips do not congregate in the areas of highest prey density in the bay.[12] Adults have no known predators.[2] Known parasites of the blacktip shark include the copepods Pandarus sinuatus and P. smithii, and the monogeneans Dermophthirius penneri and Dionchus spp., which attach the shark's skin.[2][13][14] This species is also parasitized by nematodes in the family Philometridae, which infest the ovaries.[15]

Behaviour

Blacktip sharks are social and usually found in groups.

Like the spinner shark, the blacktip shark is known to leap out of the water and spin three or four times about its axis before landing. Some of these jumps are the end product of feeding runs, in which the shark corkscrews vertically through schools of small fish and its momentum launches it into the air.[3] Observations in the Bahamas suggest that blacktip sharks may also jump out of the water to dislodge attached sharksuckers (Echeneis naucrates), which irritate the shark's skin and compromise its hydrodynamic shape.[16] The speed attained by the shark during these jumps has been estimated to average 6.3 m/s (21 ft/s).[17]

Blacktip sharks have a timid disposition and consistently lose out to Galapagos sharks (C. galapagensis) and silvertip sharks (C. albimarginatus) of equal size when competing for food.[1] If threatened or challenged, they may perform an agonistic display: the shark swims towards the threat and then turns away, while rolling from side to side, lowering its pectoral fins, tilting its head and tail upwards, and making sideways biting motions. The entire sequence lasts around 25 seconds. This behavior is similar to the actions of a shark attempting to move a sharksucker; one of these behaviors possibly is derived from the other.[18]

Feeding

Fish make up some 90% of the blacktip shark's diet.[19] A wide variety of fish have been recorded as prey for this species: sardines, herring, anchovies, ladyfish, sea catfish, cornetfish, flatfish, threadfins, mullet, mackerel, jacks, groupers, snook, porgies, mojarras, emperors, grunts, butterfish, tilapia, triggerfish, boxfish, and porcupinefish. They also feed on rays and skates, as well as smaller sharks such as smoothhounds and sharpnose sharks. Crustaceans and cephalopods are occasionally taken.[1] In the Gulf of Mexico, the most important prey of the blacktip shark is the Gulf menhaden (Brevoortia patronus), followed by the Atlantic croaker (Micropogonias undulatus).[19] Off South Africa, jacks and herring are the most important prey.[20] Hunting peaks at dawn and dusk.[19] The excitability and sociability of blacktip sharks makes them prone to feeding frenzies when large quantities of food are suddenly available, such as when fishing vessels dump their refuse overboard.[1]

Life history

As with other requiem sharks, the blacktip shark exhibits vivipary. Females typically give birth to four to seven (range one to 10) pups every other year, making use of shallow coastal nurseries that offer plentiful food and fewer predators.[1] Known nurseries include Pine Island Sound, Terra Ceia Bay, and Yankeetown along the Gulf Coast of Florida, Bulls Bay on the coast of South Carolina, and Pontal do Paraná on the coast of Brazil.[21][22] Although adult blacktip sharks are highly mobile and disperse over long distances, they are philopatric and return to their original nursery areas to give birth. This results in a series of genetically distinct breeding stocks that overlap in geographic range.[21][23]

Mating occurs from spring to early summer, and the young are born around the same time the following year after a gestation period of 10–12 months.[1] Females have one functional ovary and two functional uteri; each uterus is separated into compartments with a single embryo inside each.[24] The embryos are initially sustained by a yolk sac; in the 10th or 11th week of gestation, when the embryo measures 18–19 cm long (7.1–7.5 in), the supply of yolk is exhausted and the yolk sac develops into a placental connection that sustains the embryo until birth.[10] The length at birth is 55–60 cm (22–24 in) off the eastern United States and 61–65 cm (24–26 in) off North Africa.[10][24] The mortality rate in the first 15 months of life is 61–91%, with major threats being predation and starvation.[25] The young remain in the nurseries until their first fall, when they migrate to their wintering grounds.[10]

The growth rate of this species slows with age: 25–30 cm (9.8–11.8 in) in the first six months, then 20 cm (7.9 in) a year until the second year, then 10 cm (3.9 in) a year until maturation, then 5 cm (2.0 in) a year for adults.[26][27] The size at maturity varies geographically: males and females mature at 1.4–1.5 m (4.6–4.9 ft) and 1.6 m (5.2 ft), respectively, in the northeastern Atlantic,[10] 1.3–1.4 m (4.3–4.6 ft) and 1.5–1.6 m (4.9–5.2 ft), respectively, in the Gulf of Mexico,[26][28] 1.5 and 1.6 m (4.9 and 5.2 ft) respectively off South Africa,[29] and 1.7 and 1.8 m (5.6 and 5.9 ft), respectively, off North Africa.[24] The age at maturation is 4–5 years for males and 7–8 years for females.[26][28] The lifespan is at least 12 years.[1]

In 2007, a 9-year-old female blacktip shark at the Virginia Aquarium and Marine Science Center was found to be pregnant with a single near-term female pup, despite having never mated with a male. Genetic analysis confirmed that her offspring was the product of automictic parthenogenesis, a form of asexual reproduction in which an ovum merges with a polar body to form a zygote without fertilization. Along with an earlier case of parthenogenesis in the bonnethead (Sphyrna tiburo), this event suggests that asexual reproduction may be more widespread in sharks than previously thought.[30]

Human interactions

The blacktip shark usually poses little danger to divers.

Blacktip sharks showing curiosity towards divers has been reported, but they remain at a safe distance. Under most circumstances, these timid sharks are not regarded as highly dangerous to humans. However, they may become aggressive in the presence of food, and their size and speed invite respect.[1] As of 2008, the International Shark Attack File lists 28 unprovoked attacks (one fatal) and 13 provoked attacks by this species.[31] Blacktip sharks are responsible annually for 16% of the shark attacks around Florida. Most attacks by this species result in only minor wounds.[2]

As one of the most common large sharks in coastal waters, the blacktip shark is caught in large numbers by commercial fisheries throughout the world, using longlines, fixed-bottom nets, bottom trawls, and hook-and-line. The meat is of high quality and marketed fresh, frozen, or dried and salted. In addition, the fins are used for shark fin soup, the skin for leather, the liver oil for vitamins, and the carcasses for fishmeal.[1] Blacktip sharks are one of the most important species to the northwestern Atlantic shark fishery, second only to the sandbar shark (C. plumbeus). The flesh is considered superior to that of the sandbar shark, resulting in the sandbar and other requiem shark species being sold under the name "blacktip shark" in the United States. The blacktip shark is also very significant to Indian and Mexican fisheries, and is caught in varying numbers by fisheries in the Mediterranean and South China Seas, and off northern Australia.[27]

The blacktip shark is popular with recreational anglers in Florida, the Caribbean, and South Africa. It is listed as a game fish by the International Game Fish Association. Once hooked, this species is a strong, steady fighter that sometimes jumps out of the water.[2] Since 1995, the number of blacktip sharks taken by recreational anglers in the United States has approached or surpassed the number taken by commercial fishing.[27] The International Union for Conservation of Nature has assessed the blacktip shark as Near Threatened, as its low reproductive rate renders it vulnerable to overfishing.[32] The United States and Australia are the only two countries that manage fisheries catching blacktip sharks. In both cases, regulation occurs under umbrella management schemes for multiple shark species, such as that for the large coastal sharks category of the US National Marine Fisheries Service Atlantic shark Fisheries Management Plan. No conservation plans specifically for this species have been implemented.[27]

References

  1. ^ a b c d e f g h i j k l m n o Compagno, L.J.V. (1984). Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date. Rome: Food and Agricultural Organization. pp. 481–483. ISBN 92-5-101384-5. 
  2. ^ a b c d e f Curtis, T. Biological Profiles: Blacktip Shark. Florida Museum of Natural History Ichthyology Department. Retrieved on April 27, 2009.
  3. ^ a b c d Ebert, D.A. (2003). Sharks, Rays, and Chimaeras of California. London: University of California Press. pp. 156–157. ISBN 0-520-23484-7. 
  4. ^ a b c Froese, Rainer and Pauly, Daniel, eds. (2009). "Carcharhinus limbatus" in FishBase. April 2009 version.
  5. ^ Dosay-Akbulut, M. (2008). "The phylogenetic relationship within the genus Carcharhinus". Comptes Rendus Biologies. 331 (7): 500–509. doi:10.1016/j.crvi.2008.04.001. PMID 18558373. 
  6. ^ Keeney, D.B. & Heist, E.J. (October 2006). "Worldwide phylogeography of the blacktip shark (Carcharhinus limbatus) inferred from mitochondrial DNA reveals isolation of western Atlantic populations coupled with recent Pacific dispersal". Molecular Ecology. 15 (12): 3669–3679. doi:10.1111/j.1365-294X.2006.03036.x. PMID 17032265. 
  7. ^ Benson. R.N., ed. (1998). Geology and Paleontology of the Lower Miocene Pollack Farm Fossil Site, Delaware: Delaware Geological Survey Special Publication No. 21. Delaware Natural History Survey. pp. 133–139. 
  8. ^ Brown, R.C. (2008). Florida's Fossils: Guide to Location, Identification, and Enjoyment (third ed.). Pineapple Press Inc. p. 100. ISBN 1-56164-409-9. 
  9. ^ Martin, R.A. Albinism in Sharks. ReefQuest Centre for Shark Research. Retrieved on April 28, 2009.
  10. ^ a b c d e Castro, J.I. (November 1996). "Biology of the blacktip shark, Carcharhinus limbatus, off the southeastern United States". Bulletin of Marine Science. 59 (3): 508–522. 
  11. ^ Heupel, M.R. & Simpfendorfer, C.A. (2005). "Quantitative analysis of aggregation behavior in juvenile blacktip sharks". Marine Biology. 147 (5): 1239–1249. doi:10.1007/s00227-005-0004-7. 
  12. ^ Heupel, M.R. & Hueter, R.E. (2002). "The importance of prey density in relation to the movement patterns of juvenile sharks within a coastal nursery area". Marine and Freshwater Research. 53 (2): 543–550. doi:10.1071/MF01132. 
  13. ^ Bullard, S.A.; Frasca, A. (Jr.) & Benz, G.W. (June 2000). "Skin Lesions Caused by Dermophthirius penneri (Monogenea: Microbothriidae) on Wild-Caught Blacktip Sharks (Carcharhinus limbatus)". Journal of Parasitology. 86 (3): 618–622. doi:10.1645/0022-3395(2000)086[0618:SLCBDP]2.0.CO;2. PMID 10864264.  CS1 maint: Date and year (link)
  14. ^ Bullard, S.A.; Benz, G.W. & Braswell, J.S. (2000). "Dionchus postoncomiracidia (Monogenea: Dionchidae) from the skin of blacktip sharks, Carcharhinus limbatus (Carcharhinidae)". Journal of Parasitology. 86 (2): 245–250. doi:10.1645/0022-3395(2000)086[0245:DPMDFT]2.0.CO;2. JSTOR 3284763. PMID 10780540. 
  15. ^ Rosa-Molinar, E. & Williams, C.S. (1983). "Larval nematodes (Philometridae) in granulomas in ovaries of blacktip sharks, Carcharhinus limbatus (Valenciennes)". Journal of Wildlife Diseases. 19 (3): 275–277. doi:10.7589/0090-3558-19.3.275. PMID 6644926. 
  16. ^ Riner, E.K. & Brijnnschweiler, J.M. (2003). "Do sharksuckers, Echeneis naucrates, induce jump behaviour in blacktip sharks, Carcharhinus limbatus?". Marine and Freshwater Behaviour and Physiology. 36 (2): 111–113. doi:10.1080/1023624031000119584. 
  17. ^ Brunnschweiler, J.M. (2005). "Water-escape velocities in jumping blacktip sharks". Journal of the Royal Society Interface. 2 (4): 389–391. doi:10.1098/rsif.2005.0047. PMC 1578268Freely accessible. PMID 16849197. 
  18. ^ Ritter, E.K. & Godknecht, A.J. (February 1, 2000). Ross, S. T., ed. "Agonistic Displays in the Blacktip Shark (Carcharhinus limbatus)". Copeia. 2000 (1): 282–284. doi:10.1643/0045-8511(2000)2000[0282:ADITBS]2.0.CO;2. JSTOR 1448264.  CS1 maint: Date and year (link)
  19. ^ a b c Barry, K.P. (2002). Feeding habits of blacktip sharks, Carcharhinus limbatus, and Atlantic sharpnose sharks, Rhizoprionodon terraenovae, in Louisiana coastal waters. MS thesis, Louisiana State University, Baton Rouge.
  20. ^ Dudley, S.F.J. & Cliff, G. (1993). "Sharks caught in the protective gill nets off Natal, South Africa. 7. The blacktip shark Carcharhinus limbatus (Valenciennes)". African Journal of Marine Science. 13: 237–254. doi:10.2989/025776193784287356. 
  21. ^ a b Keeney, D.B.; Heupel, M.; Hueter, R.E. & Heist, E.J. (2003). "Genetic heterogeneity among blacktip shark, Carcharhinus limbatus, continental nurseries along the U.S. Atlantic and Gulf of Mexico". Marine Biology. 143 (6): 1039–1046. doi:10.1007/s00227-003-1166-9. 
  22. ^ Bornatowski, H. (2008). "A parturition and nursery area for Carcharhinus limbatus (Elasmobranchii, Carcharhinidae) off the coast of Paraná, Brazil". Brazilian Journal of Oceanography. 56 (4): 317–319. doi:10.1590/s1679-87592008000400008. 
  23. ^ Keeney, D.B.; Heupel, M.R.; Hueter, R.E. & Heist, E.J. (2005). "Microsatellite and mitochondrial DNA analyses of the genetic structure of blacktip shark (Carcharhinus limbatus) nurseries in the northwestern Atlantic, Gulf of Mexico, and Caribbean Sea". Molecular Ecology. 14 (7): 1911–1923. doi:10.1111/j.1365-294X.2005.02549.x. PMID 15910315. 
  24. ^ a b c Capapé, C.H.; Seck, A.A.; Diatta, Y.; Reynaud, C.H.; Hemida, F. & Zaouali, J. (2004). "Reproductive biology of the blacktip shark, Carcharhinus limbatus (Chondrichthyes: Carcharhinidae) off West and North African Coasts" (PDF). Cybium. 28 (4): 275–284. 
  25. ^ Heupel, M.R. & Simpfendorfer, C.A. (2002). "Estimation of mortality of juvenile blacktip sharks, Carcharhinus limbatus, within a nursery area using telemetry data". Canadian Journal of Fisheries and Aquatic Sciences. 59 (4): 624–632. doi:10.1139/f02-036. 
  26. ^ a b c Branstetter, S. (December 9, 1987). "Age and Growth Estimates for Blacktip, Carcharhinus limbatus, and Spinner, C. brevipinna, Sharks from the Northwestern Gulf of Mexico". Copeia. American Society of Ichthyologists and Herpetologists. 1987 (4): 964–974. doi:10.2307/1445560. JSTOR 1445560. 
  27. ^ a b c d Fowler, S.L.; Cavanagh, R.D.; Camhi, M.; Burgess, G.H.; Cailliet, G.M.; Fordham, S.V.; Simpfendorfer, C.A. & Musick, J.A. (2005). Sharks, Rays and Chimaeras: The Status of the Chondrichthyan Fishes. International Union for Conservation of Nature and Natural Resources. pp. 106–109, 293–295. ISBN 2-8317-0700-5. 
  28. ^ a b Killam, K.A. & Parsons, G.R. (May 1989). "Age and Growth of the Blacktip Shark, Carcharhinus limbatus, near Tampa Bay" (PDF). Florida Fishery Bulletin. 87: 845–857. 
  29. ^ Wintner, S.P. & Cliff, G. (1996). "Age and growth determination of the blacktip shark, Carcharhinus limbatus, from the east coast of South Africa" (PDF). Fishery Bulletin. 94 (1): 135–144. 
  30. ^ Chapman, D.D.; Firchau, B. & Shivji, M.S. (2008). "Parthenogenesis in a large-bodied requiem shark, the blacktip Carcharhinus limbatus". Journal of Fish Biology. 73 (6): 1473–1477. doi:10.1111/j.1095-8649.2008.02018.x. 
  31. ^ ISAF Statistics on Attacking Species of Shark. International Shark Attack File, Florida Museum of Natural History, University of Florida. Retrieved on April 22, 2009.
  32. ^ Musick, J.A.; Fowler, S. (2000). "Carcharhinus limbatus". IUCN Red List of Threatened Species. Version 2007. International Union for Conservation of Nature. Retrieved April 27, 2009. 
source: http://en.wikipedia.org/wiki/Blacktip_shark

Blacktip Shark 1

Blacktip Shark by Inked Animal

Blacktip Shark | Carcharhinus limbatus

 


Blacktip Shark info via Wikipedia:

Not to be confused with the blacktip reef shark, Carcharhinus melanopterus.
Blacktip shark
Carcharhinus limbatus (2).jpg
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Superorder: Selachimorpha
Order: Carcharhiniformes
Family: Carcharhinidae
Genus: Carcharhinus
Species: C. limbatus
Binomial name
Carcharhinus limbatus
(J. P. Müller & Henle, 1839)
Carcharhinus limbatus distmap.png
Range of the blacktip shark
Synonyms

Carcharias abbreviatus Klunzinger, 1871
Carcharias aethalorus Jordan & Gilbert, 1882
Carcharias ehrenbergi Klunzinger, 1871
Carcharias maculipinna Günther, 1868
Carcharias microps Lowe, 1841
Carcharias muelleri Steindachner, 1867
Carcharias phorcys Jordan & Evermann, 1903
Carcharias pleurotaenia Bleeker, 1852
Carcharhinus natator Meek & Hildebrand, 1923

The blacktip shark (Carcharhinus limbatus) is a species of requiem shark, and part of the family Carcharhinidae. It is common to coastal tropical and subtropical waters around the world, including brackish habitats. Genetic analyses have revealed substantial variation within this species, with populations from the western Atlantic Ocean isolated and distinct from those in the rest of its range. The blacktip shark has a stout, fusiform body with a pointed snout, long gill slits, and no ridge between the dorsal fins. Most individuals have black tips or edges on the pectoral, dorsal, pelvic, and caudal fins. It usually attains a length of 1.5 m (4.9 ft).

Swift, energetic piscivores, blacktip sharks are known to make spinning leaps out of the water while attacking schools of small fish. Their demeanor has been described as "timid" compared to other large requiem sharks. Both juveniles and adults form groups of varying size. Like other members of its family, the blacktip shark is viviparous; females bear one to 10 pups every other year. Young blacktip sharks spend the first months of their lives in shallow nurseries, and grown females return to the nurseries where they were born to give birth themselves. In the absence of males, females are also capable of asexual reproduction.

Normally wary of humans, blacktip sharks can become aggressive in the presence of food and have been responsible for a number of attacks on people. This species is of importance to both commercial and recreational fisheries across many parts of its range, with its meat, skin, fins, and liver oil used. It has been assessed as Near Threatened by the IUCN, on the basis of its low reproductive rate and high value to fishers.

Taxonomy

The blacktip shark was first described by French zoologist Achille Valenciennes as Carcharias (Prionodon) limbatus in Johannes Müller and Friedrich Henle's 1839 Systematische Beschreibung der Plagiostomen. The type specimens were two individuals caught off Martinique, both of which have since been lost. Later authors moved this species to the genus Carcharhinus.[1][2] The specific epithet limbatus is Latin for "bordered", referring to the black edges of this shark's fins.[3] Other common names used for the blacktip shark include blackfin shark, blacktip whaler, common or small blacktip shark, grey shark, and spotfin ground shark.[4]

Phylogeny and evolution

The closest relatives of the blacktip shark were originally thought to be the graceful shark (C. amblyrhynchoides) and the spinner shark (C. brevipinna), due to similarities in morphology and behavior. However, this interpretation has not been borne out by studies of mitochondrial and ribosomal DNA, which instead suggest affinity with the blacknose shark (C. acronotus). More work is required to fully resolve the relationship between the blacktip shark and other Carcharhinus species.[5]

Analysis of mitochondrial DNA has also revealed two distinct lineages within this species, one occupying the western Atlantic and the other occupying the eastern Atlantic, Indian, and Pacific Oceans. This suggests that Indo-Pacific blacktip sharks are descended from those in the eastern Atlantic, while the western Atlantic sharks became isolated by the widening Atlantic Ocean on one side and the formation of the Isthmus of Panama on the other. Blacktip sharks from these two regions differ in morphology, coloration, and life history characteristics, and the eastern Atlantic lineage may merit species status.[6] Fossil teeth belonging to this species have been found in Early Miocene (23–16 Ma) deposits in Delaware and Florida.[7][8]

Description

The blacktip shark has a robust, streamlined body with a long, pointed snout and relatively small eyes. The five pairs of gill slits are longer than those of similar requiem shark species.[1] The jaws contain 15 tooth rows on either side, with two symphysial teeth (at the jaw midline) in the upper jaw and one symphysial tooth in the lower jaw. The teeth are broad-based with a high, narrow cusp and serrated edges.[2] The first dorsal fin is tall and falcate (sickle-shaped) with a short free rear tip; no ridge runs between the first and second dorsal fins. The large pectoral fins are falcate and pointed.[1]

The coloration is gray to brown above and white below, with a conspicuous white stripe running along the sides. The pectoral fins, second dorsal fin, and the lower lobe of the caudal fin usually have black tips. The pelvic fins and rarely the anal fin may also be black-tipped. The first dorsal fin and the upper lobe of the caudal fin typically have black edges.[1] Some larger individuals have unmarked or nearly unmarked fins.[3] Blacktip sharks can temporarily lose almost all their colors during blooms, or "whitings", of coccolithophores.[9] This species attains a maximum known length of 2.8 m (9.2 ft), though 1.5 m (4.9 ft) is more typical, and a maximum known weight of 123 kg (271 lb).[4]

Distribution and habitat

A blacktip shark swimming in murky water off Oahu, Hawaii

The blacktip shark has a worldwide distribution in tropical and subtropical waters. In the Atlantic, it is found from Massachusetts to Brazil, including the Gulf of Mexico and the Caribbean Sea, and from the Mediterranean Sea, Madeira, and the Canary Islands to the Democratic Republic of the Congo. It occurs all around the periphery of the Indian Ocean, from South Africa and Madagascar to the Arabian Peninsula and the Indian subcontinent, to Southeast Asia. In the western Pacific, it is found from southern China to northern Australia, including the Philippines and Indonesia. In the eastern Pacific, it occurs from Baja California to Peru. It has also been reported at a number of Pacific islands, including New Caledonia, Tahiti, the Marquesas, Hawaii, Revillagigedo, and the Galápagos.[1]

Most blacktip sharks are found in water less than 30 m (98 ft) deep over continental and insular shelves, though they may dive to 64 m (210 ft).[4] Favored habitats are muddy bays, island lagoons, and the drop-offs near coral reefs; they are also tolerant of low salinity and enter estuaries and mangrove swamps. Although an individual may be found some distance offshore, blacktip sharks do not inhabit oceanic waters.[1] Seasonal migration has been documented for the population off the east coast of the United States, moving north to North Carolina in the summer and south to Florida in the winter.[10]

Biology and ecology

The blacktip shark is an extremely fast, energetic predator that is usually found in groups of varying size.[3] Segregation by sex and age does not occur; adult males and nonpregnant females are found apart from pregnant females, and both are separated from juveniles.[1] In Terra Ceia Bay, Florida, a nursery area for this species, juvenile blacktips form aggregations during the day and disperse at night. They aggregate most strongly in the early summer when the sharks are youngest, suggesting that they are seeking refuge from predators (mostly larger sharks) in numbers.[11] Predator avoidance may also be the reason why juvenile blacktips do not congregate in the areas of highest prey density in the bay.[12] Adults have no known predators.[2] Known parasites of the blacktip shark include the copepods Pandarus sinuatus and P. smithii, and the monogeneans Dermophthirius penneri and Dionchus spp., which attach the shark's skin.[2][13][14] This species is also parasitized by nematodes in the family Philometridae, which infest the ovaries.[15]

Behaviour

Blacktip sharks are social and usually found in groups.

Like the spinner shark, the blacktip shark is known to leap out of the water and spin three or four times about its axis before landing. Some of these jumps are the end product of feeding runs, in which the shark corkscrews vertically through schools of small fish and its momentum launches it into the air.[3] Observations in the Bahamas suggest that blacktip sharks may also jump out of the water to dislodge attached sharksuckers (Echeneis naucrates), which irritate the shark's skin and compromise its hydrodynamic shape.[16] The speed attained by the shark during these jumps has been estimated to average 6.3 m/s (21 ft/s).[17]

Blacktip sharks have a timid disposition and consistently lose out to Galapagos sharks (C. galapagensis) and silvertip sharks (C. albimarginatus) of equal size when competing for food.[1] If threatened or challenged, they may perform an agonistic display: the shark swims towards the threat and then turns away, while rolling from side to side, lowering its pectoral fins, tilting its head and tail upwards, and making sideways biting motions. The entire sequence lasts around 25 seconds. This behavior is similar to the actions of a shark attempting to move a sharksucker; one of these behaviors possibly is derived from the other.[18]

Feeding

Fish make up some 90% of the blacktip shark's diet.[19] A wide variety of fish have been recorded as prey for this species: sardines, herring, anchovies, ladyfish, sea catfish, cornetfish, flatfish, threadfins, mullet, mackerel, jacks, groupers, snook, porgies, mojarras, emperors, grunts, butterfish, tilapia, triggerfish, boxfish, and porcupinefish. They also feed on rays and skates, as well as smaller sharks such as smoothhounds and sharpnose sharks. Crustaceans and cephalopods are occasionally taken.[1] In the Gulf of Mexico, the most important prey of the blacktip shark is the Gulf menhaden (Brevoortia patronus), followed by the Atlantic croaker (Micropogonias undulatus).[19] Off South Africa, jacks and herring are the most important prey.[20] Hunting peaks at dawn and dusk.[19] The excitability and sociability of blacktip sharks makes them prone to feeding frenzies when large quantities of food are suddenly available, such as when fishing vessels dump their refuse overboard.[1]

Life history

As with other requiem sharks, the blacktip shark exhibits vivipary. Females typically give birth to four to seven (range one to 10) pups every other year, making use of shallow coastal nurseries that offer plentiful food and fewer predators.[1] Known nurseries include Pine Island Sound, Terra Ceia Bay, and Yankeetown along the Gulf Coast of Florida, Bulls Bay on the coast of South Carolina, and Pontal do Paraná on the coast of Brazil.[21][22] Although adult blacktip sharks are highly mobile and disperse over long distances, they are philopatric and return to their original nursery areas to give birth. This results in a series of genetically distinct breeding stocks that overlap in geographic range.[21][23]

Mating occurs from spring to early summer, and the young are born around the same time the following year after a gestation period of 10–12 months.[1] Females have one functional ovary and two functional uteri; each uterus is separated into compartments with a single embryo inside each.[24] The embryos are initially sustained by a yolk sac; in the 10th or 11th week of gestation, when the embryo measures 18–19 cm long (7.1–7.5 in), the supply of yolk is exhausted and the yolk sac develops into a placental connection that sustains the embryo until birth.[10] The length at birth is 55–60 cm (22–24 in) off the eastern United States and 61–65 cm (24–26 in) off North Africa.[10][24] The mortality rate in the first 15 months of life is 61–91%, with major threats being predation and starvation.[25] The young remain in the nurseries until their first fall, when they migrate to their wintering grounds.[10]

The growth rate of this species slows with age: 25–30 cm (9.8–11.8 in) in the first six months, then 20 cm (7.9 in) a year until the second year, then 10 cm (3.9 in) a year until maturation, then 5 cm (2.0 in) a year for adults.[26][27] The size at maturity varies geographically: males and females mature at 1.4–1.5 m (4.6–4.9 ft) and 1.6 m (5.2 ft), respectively, in the northeastern Atlantic,[10] 1.3–1.4 m (4.3–4.6 ft) and 1.5–1.6 m (4.9–5.2 ft), respectively, in the Gulf of Mexico,[26][28] 1.5 and 1.6 m (4.9 and 5.2 ft) respectively off South Africa,[29] and 1.7 and 1.8 m (5.6 and 5.9 ft), respectively, off North Africa.[24] The age at maturation is 4–5 years for males and 7–8 years for females.[26][28] The lifespan is at least 12 years.[1]

In 2007, a 9-year-old female blacktip shark at the Virginia Aquarium and Marine Science Center was found to be pregnant with a single near-term female pup, despite having never mated with a male. Genetic analysis confirmed that her offspring was the product of automictic parthenogenesis, a form of asexual reproduction in which an ovum merges with a polar body to form a zygote without fertilization. Along with an earlier case of parthenogenesis in the bonnethead (Sphyrna tiburo), this event suggests that asexual reproduction may be more widespread in sharks than previously thought.[30]

Human interactions

The blacktip shark usually poses little danger to divers.

Blacktip sharks showing curiosity towards divers has been reported, but they remain at a safe distance. Under most circumstances, these timid sharks are not regarded as highly dangerous to humans. However, they may become aggressive in the presence of food, and their size and speed invite respect.[1] As of 2008, the International Shark Attack File lists 28 unprovoked attacks (one fatal) and 13 provoked attacks by this species.[31] Blacktip sharks are responsible annually for 16% of the shark attacks around Florida. Most attacks by this species result in only minor wounds.[2]

As one of the most common large sharks in coastal waters, the blacktip shark is caught in large numbers by commercial fisheries throughout the world, using longlines, fixed-bottom nets, bottom trawls, and hook-and-line. The meat is of high quality and marketed fresh, frozen, or dried and salted. In addition, the fins are used for shark fin soup, the skin for leather, the liver oil for vitamins, and the carcasses for fishmeal.[1] Blacktip sharks are one of the most important species to the northwestern Atlantic shark fishery, second only to the sandbar shark (C. plumbeus). The flesh is considered superior to that of the sandbar shark, resulting in the sandbar and other requiem shark species being sold under the name "blacktip shark" in the United States. The blacktip shark is also very significant to Indian and Mexican fisheries, and is caught in varying numbers by fisheries in the Mediterranean and South China Seas, and off northern Australia.[27]

The blacktip shark is popular with recreational anglers in Florida, the Caribbean, and South Africa. It is listed as a game fish by the International Game Fish Association. Once hooked, this species is a strong, steady fighter that sometimes jumps out of the water.[2] Since 1995, the number of blacktip sharks taken by recreational anglers in the United States has approached or surpassed the number taken by commercial fishing.[27] The International Union for Conservation of Nature has assessed the blacktip shark as Near Threatened, as its low reproductive rate renders it vulnerable to overfishing.[32] The United States and Australia are the only two countries that manage fisheries catching blacktip sharks. In both cases, regulation occurs under umbrella management schemes for multiple shark species, such as that for the large coastal sharks category of the US National Marine Fisheries Service Atlantic shark Fisheries Management Plan. No conservation plans specifically for this species have been implemented.[27]

References

  1. ^ a b c d e f g h i j k l m n o Compagno, L.J.V. (1984). Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date. Rome: Food and Agricultural Organization. pp. 481–483. ISBN 92-5-101384-5. 
  2. ^ a b c d e f Curtis, T. Biological Profiles: Blacktip Shark. Florida Museum of Natural History Ichthyology Department. Retrieved on April 27, 2009.
  3. ^ a b c d Ebert, D.A. (2003). Sharks, Rays, and Chimaeras of California. London: University of California Press. pp. 156–157. ISBN 0-520-23484-7. 
  4. ^ a b c Froese, Rainer and Pauly, Daniel, eds. (2009). "Carcharhinus limbatus" in FishBase. April 2009 version.
  5. ^ Dosay-Akbulut, M. (2008). "The phylogenetic relationship within the genus Carcharhinus". Comptes Rendus Biologies. 331 (7): 500–509. doi:10.1016/j.crvi.2008.04.001. PMID 18558373. 
  6. ^ Keeney, D.B. & Heist, E.J. (October 2006). "Worldwide phylogeography of the blacktip shark (Carcharhinus limbatus) inferred from mitochondrial DNA reveals isolation of western Atlantic populations coupled with recent Pacific dispersal". Molecular Ecology. 15 (12): 3669–3679. doi:10.1111/j.1365-294X.2006.03036.x. PMID 17032265. 
  7. ^ Benson. R.N., ed. (1998). Geology and Paleontology of the Lower Miocene Pollack Farm Fossil Site, Delaware: Delaware Geological Survey Special Publication No. 21. Delaware Natural History Survey. pp. 133–139. 
  8. ^ Brown, R.C. (2008). Florida's Fossils: Guide to Location, Identification, and Enjoyment (third ed.). Pineapple Press Inc. p. 100. ISBN 1-56164-409-9. 
  9. ^ Martin, R.A. Albinism in Sharks. ReefQuest Centre for Shark Research. Retrieved on April 28, 2009.
  10. ^ a b c d e Castro, J.I. (November 1996). "Biology of the blacktip shark, Carcharhinus limbatus, off the southeastern United States". Bulletin of Marine Science. 59 (3): 508–522. 
  11. ^ Heupel, M.R. & Simpfendorfer, C.A. (2005). "Quantitative analysis of aggregation behavior in juvenile blacktip sharks". Marine Biology. 147 (5): 1239–1249. doi:10.1007/s00227-005-0004-7. 
  12. ^ Heupel, M.R. & Hueter, R.E. (2002). "The importance of prey density in relation to the movement patterns of juvenile sharks within a coastal nursery area". Marine and Freshwater Research. 53 (2): 543–550. doi:10.1071/MF01132. 
  13. ^ Bullard, S.A.; Frasca, A. (Jr.) & Benz, G.W. (June 2000). "Skin Lesions Caused by Dermophthirius penneri (Monogenea: Microbothriidae) on Wild-Caught Blacktip Sharks (Carcharhinus limbatus)". Journal of Parasitology. 86 (3): 618–622. doi:10.1645/0022-3395(2000)086[0618:SLCBDP]2.0.CO;2. PMID 10864264.  CS1 maint: Date and year (link)
  14. ^ Bullard, S.A.; Benz, G.W. & Braswell, J.S. (2000). "Dionchus postoncomiracidia (Monogenea: Dionchidae) from the skin of blacktip sharks, Carcharhinus limbatus (Carcharhinidae)". Journal of Parasitology. 86 (2): 245–250. doi:10.1645/0022-3395(2000)086[0245:DPMDFT]2.0.CO;2. JSTOR 3284763. PMID 10780540. 
  15. ^ Rosa-Molinar, E. & Williams, C.S. (1983). "Larval nematodes (Philometridae) in granulomas in ovaries of blacktip sharks, Carcharhinus limbatus (Valenciennes)". Journal of Wildlife Diseases. 19 (3): 275–277. doi:10.7589/0090-3558-19.3.275. PMID 6644926. 
  16. ^ Riner, E.K. & Brijnnschweiler, J.M. (2003). "Do sharksuckers, Echeneis naucrates, induce jump behaviour in blacktip sharks, Carcharhinus limbatus?". Marine and Freshwater Behaviour and Physiology. 36 (2): 111–113. doi:10.1080/1023624031000119584. 
  17. ^ Brunnschweiler, J.M. (2005). "Water-escape velocities in jumping blacktip sharks". Journal of the Royal Society Interface. 2 (4): 389–391. doi:10.1098/rsif.2005.0047. PMC 1578268Freely accessible. PMID 16849197. 
  18. ^ Ritter, E.K. & Godknecht, A.J. (February 1, 2000). Ross, S. T., ed. "Agonistic Displays in the Blacktip Shark (Carcharhinus limbatus)". Copeia. 2000 (1): 282–284. doi:10.1643/0045-8511(2000)2000[0282:ADITBS]2.0.CO;2. JSTOR 1448264.  CS1 maint: Date and year (link)
  19. ^ a b c Barry, K.P. (2002). Feeding habits of blacktip sharks, Carcharhinus limbatus, and Atlantic sharpnose sharks, Rhizoprionodon terraenovae, in Louisiana coastal waters. MS thesis, Louisiana State University, Baton Rouge.
  20. ^ Dudley, S.F.J. & Cliff, G. (1993). "Sharks caught in the protective gill nets off Natal, South Africa. 7. The blacktip shark Carcharhinus limbatus (Valenciennes)". African Journal of Marine Science. 13: 237–254. doi:10.2989/025776193784287356. 
  21. ^ a b Keeney, D.B.; Heupel, M.; Hueter, R.E. & Heist, E.J. (2003). "Genetic heterogeneity among blacktip shark, Carcharhinus limbatus, continental nurseries along the U.S. Atlantic and Gulf of Mexico". Marine Biology. 143 (6): 1039–1046. doi:10.1007/s00227-003-1166-9. 
  22. ^ Bornatowski, H. (2008). "A parturition and nursery area for Carcharhinus limbatus (Elasmobranchii, Carcharhinidae) off the coast of Paraná, Brazil". Brazilian Journal of Oceanography. 56 (4): 317–319. doi:10.1590/s1679-87592008000400008. 
  23. ^ Keeney, D.B.; Heupel, M.R.; Hueter, R.E. & Heist, E.J. (2005). "Microsatellite and mitochondrial DNA analyses of the genetic structure of blacktip shark (Carcharhinus limbatus) nurseries in the northwestern Atlantic, Gulf of Mexico, and Caribbean Sea". Molecular Ecology. 14 (7): 1911–1923. doi:10.1111/j.1365-294X.2005.02549.x. PMID 15910315. 
  24. ^ a b c Capapé, C.H.; Seck, A.A.; Diatta, Y.; Reynaud, C.H.; Hemida, F. & Zaouali, J. (2004). "Reproductive biology of the blacktip shark, Carcharhinus limbatus (Chondrichthyes: Carcharhinidae) off West and North African Coasts" (PDF). Cybium. 28 (4): 275–284. 
  25. ^ Heupel, M.R. & Simpfendorfer, C.A. (2002). "Estimation of mortality of juvenile blacktip sharks, Carcharhinus limbatus, within a nursery area using telemetry data". Canadian Journal of Fisheries and Aquatic Sciences. 59 (4): 624–632. doi:10.1139/f02-036. 
  26. ^ a b c Branstetter, S. (December 9, 1987). "Age and Growth Estimates for Blacktip, Carcharhinus limbatus, and Spinner, C. brevipinna, Sharks from the Northwestern Gulf of Mexico". Copeia. American Society of Ichthyologists and Herpetologists. 1987 (4): 964–974. doi:10.2307/1445560. JSTOR 1445560. 
  27. ^ a b c d Fowler, S.L.; Cavanagh, R.D.; Camhi, M.; Burgess, G.H.; Cailliet, G.M.; Fordham, S.V.; Simpfendorfer, C.A. & Musick, J.A. (2005). Sharks, Rays and Chimaeras: The Status of the Chondrichthyan Fishes. International Union for Conservation of Nature and Natural Resources. pp. 106–109, 293–295. ISBN 2-8317-0700-5. 
  28. ^ a b Killam, K.A. & Parsons, G.R. (May 1989). "Age and Growth of the Blacktip Shark, Carcharhinus limbatus, near Tampa Bay" (PDF). Florida Fishery Bulletin. 87: 845–857. 
  29. ^ Wintner, S.P. & Cliff, G. (1996). "Age and growth determination of the blacktip shark, Carcharhinus limbatus, from the east coast of South Africa" (PDF). Fishery Bulletin. 94 (1): 135–144. 
  30. ^ Chapman, D.D.; Firchau, B. & Shivji, M.S. (2008). "Parthenogenesis in a large-bodied requiem shark, the blacktip Carcharhinus limbatus". Journal of Fish Biology. 73 (6): 1473–1477. doi:10.1111/j.1095-8649.2008.02018.x. 
  31. ^ ISAF Statistics on Attacking Species of Shark. International Shark Attack File, Florida Museum of Natural History, University of Florida. Retrieved on April 22, 2009.
  32. ^ Musick, J.A.; Fowler, S. (2000). "Carcharhinus limbatus". IUCN Red List of Threatened Species. Version 2007. International Union for Conservation of Nature. Retrieved April 27, 2009. 
source: http://en.wikipedia.org/wiki/Blacktip_shark

Gafftopsail Catfish 2


Gafftopsail Catfish 2 by Inked Animal
Gafftopsail Catfish | Bagre marinus

 This Gyotaku deserves to be on a chinese restaurant’s wall.  Its very asian looking with the extremely falcate fins.  This animal was caught by either Adam or myself on a fishing trip to Matagorda Bay, one of our usual stomping grounds and sources for much of our saltwater material.  It is an interesting print, and misleading categorization, being that it doesn’t have scales.  Many catfish don’t have scales, but smooth skin which comes out in this print in an interesting way. Notice the wrinkles and paper creases.  Also, the long “swoop” from its chin back is the very long barbel that is covered in essentially taste buds.  Its what this animal uses to sense food.  If you like cats, make sure you check out Gafftop Catfish, Hardhead Catfish, and Hardhead Catfish – head.

 

 

 

 

 

 


 

Gafftopsail Catfish info via wikipedia:

Gafftopsail catfish
Bagre marinus (line art).jpg
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Siluriformes
Family: Ariidae
Genus: Bagre
Species: B. marinus
Binomial name
Bagre marinus
(Mitchill, 1815)
Synonyms

Felichthys felis (L.)[2]

The gafftopsail catfish, Bagre marinus, is found in the waters of the western central Atlantic Ocean, as well as the Gulf of Mexico and the Caribbean Sea. It has long venomous spines which can cause painful wounds. It feeds on crustaceans and other fish. The male of the species fertilizes the eggs of the female, and broods them in his mouth until they hatch. The gafftopsail feeds throughout the water column. This fish is a common catch in the Southeastern US, although it may be found as far north as New York. In fishing, they are considered strong fighters. They are taken from piers, jetties, reefs, and the surf, as well as bottom fishing or flats fishing. They are caught with lures, cut bait, and shrimp, as well as soft plastics. Some fishermen use traps for catfish, which is regulated by some states.

Distribution

It lives on the Atlantic, Caribbean and Gulf of Mexico coastlines from Cape Cod to Brazil.[1] It is also found in brackish waters, including estuaries, lagoons, brackish seas, and mangroves. It is generally common to abundant in its range.[1]

Characteristics

The gafftopsail catfish is blue-grey to dark brown with a light grey belly. Its appearance is typical for a catfish except for the deeply forked tail and the venomous, serrated spines. It also has a little hump that looks somewhat like a wave. The typical length of a mature gafftopsail catfish is about 17 in (43 cm). The anal fin is a few inches anterior to the tail and is white or pale blue, with 22-28 rays on it and a high, anterior lobe.[3] The pelvic fin is 6–12 in (15–30 cm) anterior to the tail fin. The gafftopsail catfish has maxillary barbels and one pair of barbels on the chin. It resembles the hardhead catfish, but its dorsal spine has a distinctive fleshy extension (like the fore-and-aft topsail of a ship).

The primary food of juveniles is unidentifiable organic matter; the secondary food is fish, with smaller amounts from other trophic groups. Unlike many other catfish, which are primarily bottom feeders, the gafftopsail catfish feeds throughout the water column. It eats mostly crustaceans, including crabs, shrimp, and prawns (95% of the diet), but it will also eat worms, other invertebrates, and bony fishes (about 5% of the diet).[4] In addition to humans, predators of the gafftopsail catfish include the tiger shark and bull shark.

Gafftopsail catfish spawn over inshore mudflats during a relatively short time span (10 days) from May to August;[5] they are mouthbreeders. The eggs are about 1 in (2.5 cm) in diameter. Males keep up to 55 eggs in their mouths until they hatch. Young are about 5 cm (2 inches) long when they hatch, and the male may continue to brood them until they are up to 4 in (10 cm) long. The males do not feed while they are carrying the eggs or young.[6]

Fishing

The gafftopsail catfish is a common catch in the Southeastern United States, although it is also caught as far north as New York. They are taken from piers, jetties, reefs, and the surf, as well as bottom fishing or flats fishing. They are caught with lures such as plugs, spoons, spinners, cut bait, and shrimp, as well as soft plastic lure resembling shrimp, worms, and shad. They are attracted to the sound of struggling fish, like a popping cork creates. Catfish trapping is also used to capture them, but is regulated in some states. Catfish traps include “slat traps,” long wooden traps with an angled entrance, and wire hoop traps. Typical bait for these traps includes rotten cheese and dog food.

Gafftopsail catfish are good eating; the red lateral line should be removed to prevent “muddy taste”; however in Gafftopsail taken from southern Florida mangrove estuaries, this is seemingly unnecessary. The pectoral fins and dorsal fin contain poisonous spines; care should be used when handling this fish.

Weight and length

Growth chart

The largest recorded weight for a gafftopsail catfish is 4.5 kg (9.9 lb)[7] and 69 cm (27 in) in length.[8] A more common weight and length of gafftopsails caught is 1–2 lb (450–910 g) and 12–16 in (30–41 cm).

As gafftopsail catfish grow longer, they increase in weight, but the relationship is not linear. The relationship between total length (L, in inches) and total weight (W, in pounds) for nearly all species of fish can be expressed by an equation of the form:

W = c L b {\displaystyle W=cL^{b}\!\,} W=cL^{b}\!\,

Invariably, b is close to 3.0 for all species, and the constant ct varies between species.[9] Data from the Florida Fish and Wildlife Conservation Commission indicate, for the gafftopsail catfish, c = 0.000493 and b = 3.075[10] The relationship described in this section suggests a 12-inch gafftopsail catfish will weigh about one pound, while a 20-inch fish will likely weigh about five pounds.

References

  1. ^ a b c Chao, L., Vega-Cendejas, M., Tolan, J., Jelks, H. & Espinosa-Perez, H. (2015). "Bagre marinus". IUCN Red List of Threatened Species. Version 2017.1. International Union for Conservation of Nature. Retrieved 18 February 2017.  CS1 maint: Multiple names: authors list (link)
  2. ^ Gulf-topsail Cat, Felichthys felis (L.)
  3. ^ Smith, C. Lavett. National Audubon Society Field Guide to Tropical Marine Fishes of the Caribbean, the Gulf of Mexico, Florida, the Bahamas, and Bermuda. Chanticleer Press, 1997, ISBN 0-679-44601-X, pp. 85 & 346
  4. ^ FishBase.org: Food and Feeding Habits Summary - Bagre Marinus see online accessed 11 March 2010
  5. ^ Muncy R.J., Wingo W.M.,Species Profiles: Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (Gulf of Mexico): Sea Catfish and Gafftopsail Catfish read online p. 4
  6. ^ Smith, pp. 85 & 346
  7. ^ IGFA 2007 Database of IGFA angling records. IGFA, Ft. Lauderdale, FL, USA http://www.igfa.org/Records/Fish-Records.aspx?Fish=Catfish, gafftopsail&LC=ATR
  8. ^ Froese, Rainer and Pauly, Daniel, eds. (2017). "Bagre marinus" in FishBase. February 2017 version.
  9. ^ R. O. Anderson and R. M. Neumann, Length, Weight, and Associated Structural Indices, in Fisheries Techniques, second edition, B.E. Murphy and D.W. Willis, eds., American Fisheries Society, 1996.
  10. ^ average of data for male and female gafftopsail catfish at Florida Fish and Wildlife Conservation Commission Report 2008 accessed 7 March 2010
source: http://en.wikipedia.org/wiki/Gafftopsail_catfish

Mexican Free-tailed Bat 2

Mexican Free-tailed Bat 2 by Inked Animal

Mexican Free-tailed Bat  | Tadarida brasiliensis

 

We found this Mexican Free-tailed bat, aka Brazilian Free-tailed bat, in Austin, Texas.  There are tons of these in the city under bridges and roof eves, Austin is known for the colony under the Congress bridge, which is apparently one of the biggest, if not the biggest, urban bat colonies in the world.  They are pretty impressive.

Mexican Free-tailed Bat info via Wikipedia:

Mexican free-tailed bat
Tadarida brasiliensis
Tadarida brasiliensis.jpg
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Chiroptera
Family: Molossidae
Genus: Tadarida
Species: T. brasiliensis
Binomial name
Tadarida brasiliensis
(I. Geoffroy, 1824)
Subspecies
  • T. b. antillularum
  • T. b. bahamensis
  • T. b. brasiliensis
  • T. b. constanzae
  • T. b. cynocephali
  • T. b. intermedia
  • T. b. mexicana
  • T. b. murina
  • T. b. muscula
Tadarida brasiliensis Range.png
Range of the Mexican free-tailed bat

The Mexican free-tailed bat or Brazilian free-tailed bat (Tadarida brasiliensis) is a medium-sized bat that is native to the Americas, regarded as one of the most abundant mammals in North America. Its proclivity towards roosting in huge numbers at relatively few locations makes it vulnerable to habitat destruction in spite of its abundance. The bat is considered a species of special concern in California as a result of declining populations. It has been claimed to have the fastest horizontal speed (as opposed to e.g. stoop diving speed) of any animal, reaching top ground speeds of over 160 km/h; its actual air speed has not been measured.

Taxonomy

Molecular sequence data indicates T. brasiliensis's closest relatives are Chaerephon jobimena of Madagascar and Tadarida aegyptiaca of Africa and south Asia; the latter two are sister species. These three species form a clade believed to be about 9.8 million years old.[2]

Physical description

Mexican free-tailed bats are on average 9 cm (3.5 in) in length and weigh approximately 12.3 g (0.43 oz). The average wingspan is 28 cm (11 in).[3] Their tail is almost half their total length and stretches beyond the uropatagium, giving them the name "free-tailed" bats. Their ears are relatively close behind the muzzle and eyes; they are wide and set apart to help them find prey using echolocation. The muzzle is condensed, with wrinkled upper lips. The wings are elongated and narrow with pointed tips, making them well-equipped for quick, straight flight patterns. Their fur color ranges from dark brown to gray.

Range and ecology

Bats flying near Frio Cave in Concan, Texas

The Mexican free-tailed bat ranges from the southern half of the continental United States through most of Mexico, and through most of Central America into South America. The range of the Mexican free-tailed bat in South America is less understood where it lives in the eastern Brazilian highlands and coast, the northeastern Andes and the coast of Peru and northern Chile.[4] It is absent in much of the Amazon rainforest. The bat is also found in the Caribbean, and is native to all of the Greater Antilles and 11 of the Lesser Antilles.[5] The largest known colony is found at Bracken Cave, north of San Antonio, Texas, with nearly 20 million bats; research indicates the bats from this colony congregate in huge numbers at altitudes between 180 and 1,000 m (590 and 3,280 ft), and even as high as 3,000 m (9,800 ft).

Habitat

Mexican free-tailed bats roost primarily in caves. However, they will also roost in buildings of any type as long as they have access to openings and dark recesses in ceilings or walls.[4] The bats can make roosting sites of buildings regardless of "age, height, architecture, construction materials, occupancy by humans and compass orientation".[4] Caves, on the other hand, need to have enough wall and ceiling space to fit millions of bats.[4] Before buildings, free-tailed bats in the southeastern United States probably roosted in the hollows of trees such as red mangrove, black mangrove, white mangrove and cypress. However, most bats in Florida seem to prefer buildings and other man-made structures over natural roosts.[4] Caves in Florida tend to be occupied mostly by the southeastern myotis. Caves in Florida tend to have pools of water on the floor and the free-tailed bats do not need as much relative humidity as the southeastern myotis.[4]

Migration

Mexican free-tailed bats, emerging from Carlsbad Caverns, Carlsbad Caverns National Park, New Mexico

Mexican free-tailed bats in southeastern Nevada, southwestern Utah, western Arizona and southeastern California come together to migrate southwest to southern California and Baja California.[4] Bats in southeastern Utah, southwestern Colorado, western New Mexico and eastern Arizona travel though western edge of the Sierra Madre Oriental into Jalisco, Sinaloa and Sonora. Some bats that summer in Kansas, Oklahoma, eastern New Mexico and Texas will migrate southward to southern Texas[6] and Mexico.[4] Some bat populations in other areas of North America do not migrate, but are residents and may make seasonal changes in roost sites.[4]

Dusk emergence of bats at the Congress Avenue Bridge in Austin, Texas, U.S.

In Austin, Texas, a colony of Mexican free-tailed bats summers (they winter in Mexico) under the Congress Avenue Bridge ten blocks south of the Texas State Capitol. It is the largest urban colony in North America, with an estimated 1,500,000 bats.[7] Each night they eat 10,000 to 30,000 lb (4,500 to 13,600 kg) of insects. Each year they attract 100,000 tourists who come to watch them. In Houston, Texas, a colony is living under the Waugh Street Bridge over Buffalo Bayou. It is the home to 250,000 bats and also attracts viewers. The Mexican free-tailed bat is the official "flying mammal" of the state of Texas.[8]

Bats ranging eastward from East Texas do not migrate, but local shifts in roost usage often occur seasonally.[4] Also, a regional population that ranges from Oregon to California, has a year-round residence.

Diet

The Mexican free-tailed bat features in the logo of the Bacardi company

Mexican free-tailed bats are primarily insectivores. They hunt their prey using echolocation. The bats eat moths, beetles, dragonflies, flies, true bugs, wasps, and ants. Bats usually catch flying prey in flight.[9] Large numbers of Mexican free-tailed bats fly hundreds of meters above the ground in Texas to feed on migrating insects.[10] The consumption of insects by these bats can be quite significant.[11][12]

Health and mortality

One individual bat was recorded to have lived eight years, based on dentition.[13] Predators of the bat include large birds such as red-tailed hawk, American kestrels, great horned owls, barn owls, and Mississippi kites.[4][14] Mammal predators include Virginia opossums, striped skunks, and raccoons.[4] Snakes such as eastern coachwhips and eastern coral snakes may also prey on them, but at a lesser extent. Certain types of beetles prey on neonate and juvenile bats that have fallen to the ground.[4] This species seems to have a low incidence of rabies, at least in the United States.[4] They do, however, contain certain pesticides.[4]

Behavior

A male displays and sings in the presence of females (watch in slow motion).

Mexican free-tailed bats are nocturnal foragers and begin feeding after dusk. They travel 50 km in a quick, direct flight pattern to feed. This species flies the highest among bats, at altitudes around 3300 m.[15] Bats appears to be most active in late morning and afternoon between June and September.[16] Free-tailed bats are more active in warm weather.[17]

The species has been measured at a ground speed of 160 kilometres per hour (99 mph), measured by an aircraft tracking device.[18] The measurement methodology did not simultaneously record wind speed and ground speed, so the observations could have been affected by strong local gusts, and the bat's maximum air speed remains uncertain.[19]

Echolocation

Mexican free-tailed bats use echolocation for navigation and detecting prey. Traveling calls are of a brief but constant frequency. However, they switch modulated frequency calls between 40 and 75 kHz if they detect something.[20] Typically, the frequency range of their echolocation is between 49 and 70 kHz, but can be between 25 and 40 kHz if something crosses their path while in flight.[20]

On 6 November 2014, Aaron Corcoran, a biologist at Wake Forest University, North Carolina, reported online in Science that he and his team had detected Mexican free-tailed bats emitting ultrasonic vocalizations which had the effect of jamming the echolocation calls of a rival bat species hunting moths. The ‘jamming’ call led to an increased chance of the rival missing its prey, which the Mexican free-tailed bat was then able to eat itself. Earlier researchers had discovered some 15 types of social calls made by Mexican free-tailed bats and reported that they could adjust their calls to avoid interfering with others in range of their calls.[21][22]

Mating and reproduction

Free-tailed bats roosting at a cave in the Bahamas

During the breeding season, females aggregate into maternity roosts. The size of these roosts depends on the environment, with caves having the larger roosts. Mating can occur in an aggressive or passive form. In the aggressive form, the male controls the female's movements, keeping her away from the other bats in the roost.[23] He also tends to vocalize when mating. During passive copulation, the males simply flies to a female in her roost and quietly mounts her with no resistance. This species is a promiscuous breeder and both sexes copulate with multiple partners.[23] Females become sexually mature at about 9 months, while males take even longer, at two years. Females enter estrus once a year, which typically lasts five weeks in the spring. The gestation period of the bat lasts 11–12 weeks, with only one young being born. A number of pups are left in "creches", while their mothers roost elsewhere. The female uses vocalizations and scent to identify her pup. The mother imprints her scent on the young early on.[24] However, young try to steal a suckle from any female that passes through the cluster. A mother will nurse her young daily, and by 4–7 weeks old they are full grown, fully weaned, and independent.[25]

Protection

Though abundant and widespread, some local populations have prompted protection and conservation efforts. For instance, during the spring and summer, one of the largest Mexican free-tailed bat populations inhabits Cueva de la Boca, a cave near Monterrey, Mexico. In 2006, the Mexican environmental conservation NGO, Pronatura Noreste, purchased the property. Because of a reduction of more than 95% of the original 20 million bat population, as a result of vandalism, pollution, and uncontrolled tourism, the organization decided to buy the property to place it under conservation. Other species of high ecological value that inhabit the cavern are also being protected.

See also

  • Bat bomb, an experimental incendiary weapon that used Mexican free-tailed bats as a dispersal mechanism

References

  1. ^ Barquez, R., Diaz, M., Gonzalez, E., Rodriguez, A., Incháustegui, S. & Arroyo-Cabrales, J. (2015). Tadarida brasiliensis. The IUCN Red List of Threatened Species doi:10.2305/IUCN.UK.2015-4.RLTS.T21314A22121621.en
  2. ^ Lamb, J. M.; Ralph, T. M. C.; Naidoo, T.; Taylor, P. J.; Ratrimomanarivo, F.; Stanley, W. T.; Goodman, S. M. (June 2011). "Toward a Molecular Phylogeny for the Molossidae (Chiroptera) of the Afro-Malagasy Region". Acta Chiropterologica. 13 (1): 1–16. doi:10.3161/150811011X578589. 
  3. ^ "Animal Diversity Web: Tadarida brasiliensis". Retrieved 2016-11-10. 
  4. ^ a b c d e f g h i j k l m n o Wilkins, K. (1989). "Tadarida brasiliensis" (PDF). Mammalian Species. 331: 1–10. 
  5. ^ Baker, R. J., Genoways, H. H. (1978). "Zoogeography of Antillean bats", pp. 53–97 in Zoogeography in the Caribbean, F. B. Gill (ed.). Philadelphia: Acad
  6. ^ Glass BP (1982). "Seasonal movements of Mexican free-tail bats Tadarida brasiliensis mextcana banded in the Great Plains". Southwestern Nat. 27: 127–133. 
  7. ^ "Congress Avenue Bridge". Congress Avenue Bridge Bat Colony. 
  8. ^ "Texas State Symbols". Texas State Library and Archives Commission. 
  9. ^ McWilliams, Lisa A. (2005). "Variation in Diet of the Mexican Free-Tailed Bat (Tadarida brasiliensis mexicana)". Journal of Mammalogy. 86 (3): 599. doi:10.1644/1545-1542(2005)86[599:VIDOTM]2.0.CO;2. 
  10. ^ McCracken, G. F.; Gillam, E. H.; Westbrook, J. K.; Lee, Y. F.; Jensen, M. L.; Balsley, B. B. (2008). "Brazilian free-tailed bats (Tadarida brasiliensis: Molossidae, Chiroptera) at high altitude: Links to migratory insect populations". Integrative and Comparative Biology. 48 (1): 107–18. doi:10.1093/icb/icn033. PMID 21669777. 
  11. ^ Corrigan, Robert. Do Bats Control Mosquitoes? texasmosquito.org
  12. ^ Animal Fact Sheet: Mexican Free-Tailed Bat. Desert Museum
  13. ^ Gannon, M., A. Kurta, A. Rodriquez-Duran, M. Willig. (2005). Bats of Puerto Rico. Jamaica. The University of the West Indies Press.
  14. ^ Mikula, P.; Morelli, F.; Lučan, R. K.; Jones, D. N.; Tryjanowski, P. (2016). "Bats as prey of diurnal birds: a global perspective". Mammal Review. 46 (3): 160. doi:10.1111/mam.12060. 
  15. ^ Williams, T. C.; Ireland, L. C.; Williams, J. M. (1973). "High Altitude Flights of the Free-Tailed Bat, Tadarida brasiliensis, Observed with Radar". Journal of Mammalogy. 54 (4): 807. doi:10.2307/1379076. JSTOR 1379076. 
  16. ^ Svoboda, P. L.; Choate, J. R. (1987). "Natural History of the Brazilian Free-Tailed Bat in the San Luis Valley of Colorado". Journal of Mammalogy. 68 (2): 224. doi:10.2307/1381461. JSTOR 1381461. 
  17. ^ Allen, L. C.; Turmelle, A. S.; Mendonça, M. T.; Navara, K. J.; Kunz, T. H.; McCracken, G. F. (2009). "Roosting ecology and variation in adaptive and innate immune system function in the Brazilian free-tailed bat (Tadarida brasiliensis)" (PDF). Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology. 179 (3): 315–23. doi:10.1007/s00360-008-0315-3. PMID 19002470. 
  18. ^ McCracken, Gary F.; Safi, Kamran; Kunz, Thomas H.; Dechmann, Dina K. N.; Swartz, Sharon M.; Wikelski, Martin (9 November 2016). "Airplane tracking documents the fastest flight speeds recorded for bats". Royal Society Open Science. 3 (11): 160398. doi:10.1098/rsos.160398. 
  19. ^ Photopoulos, Julianna (9 November 2016). "Speedy bat flies at 160km/h, smashing bird speed record". New Scientist. Retrieved 11 November 2016. But not everyone is convinced. Graham Taylor at the University of Oxford says that errors in estimating bat speed by measuring the distance moved between successive positions could be huge. “So I think it would be premature to knock birds off their pedestal as nature's fastest fliers just yet,” he says."These bats are indeed flying very fast at times, but this is based on their ground speed," says Anders Hedenström at the University of Lund in Sweden. "Since they did not measure winds at the place and time where the bats are flying, one can therefore not exclude that the top speeds are not bats flying in a gust." 
  20. ^ a b Gillam, Erin H.; McCracken, Gary F. (2007). "Variability in the echolocation of Tadarida brasiliensis: Effects of geography and local acoustic environment". Animal Behaviour. 74 (2): 277. doi:10.1016/j.anbehav.2006.12.006. 
  21. ^ Morell, Virginia (6 November 2014). "Holy blocked bat signal! Bats jam each other's calls". new.sciencemag.org. Retrieved 8 November 2014. 
  22. ^ Hogenboom, Melissa (7 November 2014). "Bats sabotage rivals' senses with sound in food race". BBC News. Retrieved 8 November 2014. 
  23. ^ a b Keeley, Annika T. H.; Keeley, Brian W. (2004). "The Mating System of Tadarida brasiliensis (Chiroptera: Molossidae) in a Large Highway Bridge Colony". Journal of Mammalogy. 85: 113. doi:10.1644/BME-004. 
  24. ^ Loughry, W. J.; McCracken, G. F. (1991). "Factors Influencing Female-Pup Scent Recognition in Mexican Free-Tailed Bats". Journal of Mammalogy. 72 (3): 624. doi:10.2307/1382150. JSTOR 1382150. 
  25. ^ Kunz, Thomas H.; Robson, Simon K. (1995). "Postnatal Growth and Development in the Mexican Free-Tailed Bat (Tadarida brasiliensis mexicana): Birth Size, Growth Rates, and Age Estimation" (PDF). Journal of Mammalogy. 76 (3): 769. doi:10.2307/1382746. JSTOR 1382746. 
source: http://en.wikipedia.org/wiki/Mexican_Free-tailed_Bat
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