Alligator snapping turtle

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Alligator snapping turtle
Conservation status
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Reptilia
Order:Testudines
Family:Chelydridae
Genus:Macrochelys
Gray, 1856[1]
Species:M. temminckii
Binomial name
Macrochelys temminckii
(Troost, 1835)[1]
Synonyms
 
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Alligator snapping turtle
Conservation status
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Reptilia
Order:Testudines
Family:Chelydridae
Genus:Macrochelys
Gray, 1856[1]
Species:M. temminckii
Binomial name
Macrochelys temminckii
(Troost, 1835)[1]
Synonyms

The alligator snapping turtle (Macrochelys temminckii) is one of the largest freshwater turtles in the world. It is often associated with, but not closely related to the common snapping turtle. They are the sole living member of the genus Macrochelys--while common snappers are in the genus Chelydra. The epithet temminckii is in honor of Dutch zoologist Coenraad Jacob Temminck.[4]

Contents

Distribution and habitat

The largest freshwater turtle in North America, the alligator snapping turtle is found primarily in southeasten United States waters. They are found from eastern Texas east to the Florida panhandle, and north to southeastern Kansas, Missouri, southeastern Iowa, western Illinois, southern Indiana, western Kentucky, and eastern Tennessee.[5] Typically only nesting females will venture onto open land.[citation needed]

Due to the exotic pet trade and habitat destruction the species has become protected by states, and is considered a threatened species. This endangerment brought it to Asia and Europe with a breeding/research center found in Japan.[6][not in citation given]

Description

Illustration from Holbrook's North American Herpetology, 1842

The alligator snapping turtle is characterized by a large, heavy head, and a long, thick shell with three dorsal ridges of large scales (osteoderms) giving it a primitive appearance reminiscent of some of the plated dinosaurs. They can be immediately distinguished from the Common Snapping Turtle by the three distinct rows of spikes and raised plates on the carapace, whereas the common snapping turtle has a smoother carapace. They are a solid gray, brown, black, or olive-green in color, and often covered with algae. They have radiating yellowpatterns around the eyes, serving to break up the outline of the eye and keep the turtle camouflaged. Their eyes are also surrounded by a star-shaped arrangement of fleshy filamentous "eyelashes".

There is an unverified report of a 183 kilograms (400 lb) Alligator Snapping Turtle found in Kansas in 1937,[7] but the largest verifiable one is debatable. One weighed at the Shedd Aquarium in Chicago was a 16-year resident giant alligator snapper weighing 113 kilograms (250 lb), sent to the Tennessee State Aquarium as part of a breeding loan in 1999, where it subsequently died. Another was 107 kilograms (240 lb), and housed at the Brookfield Zoo in suburban Chicago. They generally do not grow quite that large. Breeding maturity is attained at around 16 kilograms (35 lb), when the length is around 38 centimetres (15 in), but then they continue to grow through life.[8] Alligator snapping turtles generally range in carapace length from 40.4 to 80.8 centimetres (15.9 to 31.8 in) and weigh from 68 to 80 kilograms (150 to 180 lb).[9][10] Males are typically larger than females.[11] Among extant freshwater turtles, only the little-known giant softshell turtles of the genera Rafetus and Pelochelys, native to Asia, reach comparable sizes.

Head of a young alligator snapping turtle
Alligator snapping turtle with carpet of algae

In mature specimens (carapace length over 30 centimetres (12 in)) male and female can be differentiated by the position of the cloaca from the carapace and the thickness of the tail's base. A mature male's cloaca extends beyond the carapace edge, a female's is placed exactly on the edge if not nearer to the plastron. The base of the tail of the male is also thicker as compared to females because of the hidden reproductive organs.

The inside of the turtle's mouth is camouflaged, and it possesses a vermiform (literally, "worm-shaped") appendage on the tip of its tongue used to lure fish, a form of Peckhamian mimicry. The turtle hunts by lying motionless in the water with its mouth wide open. The vermiform tongue imitates the movements of a worm, luring prey to the turtle's mouth. The mouth is then closed with tremendous speed and force, completing the ambush.

Contrary to claims that alligator snapping turtles possess the second strongest bite force of any animal, it has been recorded at 158 ± 18 kilograms-force (1,550 ± 180 N; 350 ± 40 lbf) which is lower than several other species of turtle and at about the same level as humans.[12][13] Still, these turtles must be handled with extreme care.[11]

Fossil history

Unlike the family Chelydridae as a whole, the genus Macroclemmys is exclusively North American and is generally considered to contain three valid species: the extant M. temminckii and the extinct M. schmidti and M. auffenbergi (described from the early middle Miocene of Nebraska and the middle Pliocene of Florida, respectively).

Diet

Alligator snappers are opportunistic omnivores more often at a young age, but are also scavengers. Fishermen have glorified the species' ability to catch fish and to deplete fish populations. Minnows,worms,and any insect they can fit in their mouths are usually the main source of meat for the species at a young age. (except slugs)[citation needed] They will eat almost anything they can catch or fead.

Their natural diet consists primarily of fish and dead fish carcasses (usually thrown overboard by fishermen), invertebrates, carrion, and amphibians, but they are also known to eat snakes, and even other turtles. In captivity they may consume almost any kind of meat provided, including beef, chicken and pork although these are not always healthy on a day to day basis.[citation needed] They will refuse to eat if exposed to temperature extremes. Though not a primary food source for them, adult Alligator snappers have been known to kill and eat small alligators[14] that they have been confined with, such as in a net, small bog, or poorly planned aquarium display.[citation needed]

Reproduction and lifespan

Maturity is reached at around 12 years of age.[15] Mating takes place yearly; early spring in the southern part of their total range, and later spring in the north. The female builds a nest and lays a clutch of 10–50 eggs[9] about 2 months later. The gender of the baby alligator snapping turtles depends on the temperature at which the eggs are incubated. Nests are typically excavated at least 50 yards from the water's edge to prevent them from being flooded and drowned. Incubation takes from 100 to 140 days, and hatchlings emerge in the early fall.[16]

Though their potential lifespans in the wild are unknown, alligator snapping turtles are believed to be capable of living to 200 years of age but 80 to 120 is more likely. In captivity, they typically live from anywhere between 20 to 70 years of age.[17]

In captivity

Correct handling of a 45 pound alligator snapping turtle at Austin Reptile Service, in Austin, Texas.

Alligator snapping turtles are usually captive-bred as pets and are readily available in the exotic animal trade. Due to their potential size and specific needs, they do not make particularly good pets for any but the most experienced aquatic turtle keepers.[18]

They prefer to feed on live fish which they catch with their special technique but would readily feed on other types of meat or leafy vegetables if offered. Hand feeding with is dangerous, as an alligator snapping turtle is capable of removing a finger with an errant bite. Temperature extremes are known to affect the turtle's appetite and would result in the turtle refusing to feed until it has been remedied.

Due to their sheer size, handling adult specimens can pose significant problems. Small turtles can be held by the tail with relative safety, but large individuals must be held by grasping the turtle's shell just behind the head and in front of the tail.

Despite their reputation they are typically not prone to biting, but if provoked are quite capable of delivering a bite with their powerful jaws which can cause significant harm to a human, easily amputating fingers.[19] Some states where alligator snapping turtles do not naturally occur (such as California) prohibit them from being kept as pets by residents.

Conservation status

The alligator snapping turtle is primarily vulnerable to humans from habitat loss and hunting. Some are hunted for their carapaces; the plastron of the turtle is valued because of its shape as a cross. There are accounts of large (50+ lb) turtles being caught both purposely and accidentally on recreational fishing lines called "trot lines." Abandoned trot lines are thought to be even more dangerous to turtles. Soup made from snapping turtle meat is considered by some to be a delicacy.

This turtle is protected from collection throughout much of its range. The IUCN lists it as a threatened species, and as of June 14, 2006, it was afforded some international protection by being listed as a CITES 3 species (which will put limits on exportation from the United States and all international trade in this species).[20] The alligator snapping turtle is now endangered in several states, including Indiana[21] and Illinois. Illinois fishing of snapping turtles is illegal and heavily fined.

References

  1. ^ a b c Rhodin 2010, p. 000.92
  2. ^ Fritz 2007, p. 172
  3. ^ Fritz 2007, pp. 172–173
  4. ^ "Biographies of People Honored in the Herpetological Nomenclature North America". Archived from the original on 10 July 2006. http://ebeltz.net/herps/biogappx.html. Retrieved 2006-07-09. 
  5. ^ Conant, Roger; Collins, Joseph T. (1991). A Field Guide to Reptiles and Amphibians: eastern and Central North America (third ed.). Boston: Houghton Mifflin Company. ISBN 0395904528. 
  6. ^ "Wanigame mode of life laboratory (Japanese site)". wanigame.exblog.jp. http://wanigame.exblog.jp/. 
  7. ^ "Smithsonian National Zoological Park: Alligator Snapping Turtle". Archived from the original on 7 March 2006. http://nationalzoo.si.edu/Animals/ReptilesAmphibians/Facts/FactSheets/Alligatorsnappingturtle.cfm. Retrieved 2006-03-26. 
  8. ^ Alligator Snapping Turtle. People.wcsu.edu. Retrieved on 2012-08-22.
  9. ^ a b Kindersley, Dorling (2001,2005). Animal. New York City: DK Publishing. ISBN 0-7894-7764-5. 
  10. ^ Alligator Snapping Turtle – National Zoo| FONZ. Nationalzoo.si.edu. Retrieved on 2012-08-22.
  11. ^ a b "Alligator Snapping Turtle: Giant of the Southeastern States". Archived from the original on 8 April 2006. http://www.tortoise.org/archives/macrocl.html. Retrieved 2006-03-26. 
  12. ^ Herrel, A.; O'Reilly, J. C.; Richmond, A. M. (2002). "Evolution of bite performance in turtles". Journal of Evolutionary Biology 15 (6): 1083. doi:10.1046/j.1420-9101.2002.00459.x. http://webhost.ua.ac.be/funmorph/publications/Herrel%20et%20al%202002%20J%20Evol%20Biol.pdf. 
  13. ^ Braun, S; Bantleon, HP; Hnat, WP; Freudenthaler, JW; Marcotte, MR; Johnson, BE (1995). "A study of bite force, part 2: Relationship to various cephalometric measurements". The Angle orthodontist 65 (5): 373–7. doi:10.1043/0003-3219(1995)065<0373:ASOBFP>2.0.CO;2. PMID 8526297. 
  14. ^ The Bronx Zoo: Alligator Snapping Turtle. bronxzoo.com
  15. ^ "Animal Diversity Web: Macrochelys temminickii". http://animaldiversity.ummz.umich.edu/site/accounts/information/Macrochelys_temminckii.html. Retrieved 2008-09-12. 
  16. ^ "Nashville Zoo: Alligator Snapping Turtle". Archived from the original on 2006-02-21. http://web.archive.org/web/20060221084138/http://www.nashvillezoo.org/asturtle.htm. Retrieved 2006-03-26. 
  17. ^ "WhoZoo: Alligator Snapping Turtle". Archived from the original on 28 April 2006. http://www.whozoo.org/AnlifeSS2001/serishoo/SRS_AlligatorSnappingTurtle.html. Retrieved 2006-03-26. 
  18. ^ AST Care Sheet. Austinsturtlepage.com. Retrieved on 2012-08-22.
  19. ^ "NAS — Species FactSheet". http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=1227. Retrieved 2006-03-26. 
  20. ^ "Alligator Snapping Turtle and Map Turtles Gain International Protection". http://greennature.com/article2503.html. Retrieved 2006-03-26. 
  21. ^ Indiana Legislative Services Agency (2011). "312 IAC 9-5-4: Endangered species of reptiles and amphibians". Indiana Administrative Code. http://www.in.gov/legislative/iac/. Retrieved 28 Apr 2012. 

Bibliography

External links