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

The alligator snapping turtle (Macrochelys temminckii) is the largest freshwater turtle in the world based on weight[4] 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.[5]

Distribution and habitat[edit]

The alligator snapping turtle is found primarily in southeastern United States waters. They are found from East Texas east to the Florida panhandle, and north to southeastern Kansas, Missouri, southeastern Iowa, western Illinois, southern Indiana, western Kentucky, and western Tennessee.[6] Typically, only nesting females will venture onto open land.[citation needed]

Description[edit]

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 yellow patterns around their eyes, serving to break up the outline of the eyes to keep the turtle camouflaged. Their eyes are also surrounded by a star-shaped arrangement of fleshy, filamentous "eyelashes".

Though not verified, a 183 kg (403 lb) alligator snapping turtle was 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 kg (249 lb), sent to the Tennessee State Aquarium as part of a breeding loan in 1999, where it subsequently died. Another weighing 107 kg (236 lb) was housed at the Brookfield Zoo in suburban Chicago. They generally do not grow quite that large. Breeding maturity is attained at around 16 kg (35 lb), when the length is around 38 cm (15 in), but then they continue to grow through life.[8] Adult alligator snapping turtles generally range in carapace length from 40.4 to 80.8 cm (15.9 to 31.8 in) and weigh from 68 to 80 kg (150 to 176 lb).[9][10] Males are typically larger than females.[11] Among extant freshwater turtles, only the little-known giant softshell turtles of the genera Chitra, 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 cm (12 in)), males and females 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 one of the strongest bite force of any animal, it has been recorded at 158 ± 18 kgf (1,550 ± 180 N; 348 ± 40 lbf), which is lower than several other species of turtles and at about the same level as humans, relative to the turtle's body size.[12][13] Still, these turtles must be handled with extreme care and considered potentially dangerous.[11] This species can bite through the handle of a broom and rare cases have been reported where human fingers have been cleanly bitten off by the species.[14] No human deaths have been reported to have been caused by alligator snapping turtles.[14]

Although it was once believed to be only one species, a recent study suggests that it is actually three separate species.[15]

Fossil history[edit]

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). Hutchison (2008) considered genus Chelydrops to be a junior synonym of Macrochelys, and recombined its type species, Chelydrops stricta from the Miocene (early Barstovian) of Nebraska, as the fourth species of Macrochelys.[16]

Diet[edit]

Alligator snappers are opportunistic feeders that are almost entirely carnivorous. They rely on both live food caught by themselves and dead organisms which they scavenge. In general, they will eat almost anything they can catch. Fishermen have glorified the species' ability to catch fish and to deplete fish populations, whereas in fact they largely target any abundant and easily caught prey, and rarely have any extensive deleterious effect on fish populations.[17] Their natural diets consist primarily of fish and fish carcasses (often ones that are thrown back into the water by fishermen), molluscs, carrion, and amphibians, but they are also known to eat snakes, crayfish, worms, water birds, aquatic plants, and other turtles.[14][17] In one study conducted in Louisiana, 79.8% of the stomach contents of adult alligator snapping turtles was found to be comprised by other turtles.[18] This species may also, on occasion, prey on aquatic rodents, including nutrias and muskrats or even snatch small to mid-sized other mammals, including squirrels, opossums, raccoons, and armadillos when they attempt to swim or come to the water's edge.[14] Alligator snapping turtles seemingly most often hunt at night. They may also hunt diurnally, however. By day, they may try to attract fish and other prey by sitting quietly at the bottom of murky water and let their jaws hang open to reveal their tongues, which look like small, pink, worm-like lures in the back of their gray mouths, and literally lure the prey into striking distance.[17] Small fish, such as minnows, are often caught in this way by younger alligator snapping turtles, whereas adults must eat a greater quantity per day and must forage more actively.[14] Though not a regular food source for them, adult alligator snappers have even been known to kill and eat small American alligators.[19]

In captivity, they may consume almost any kind of meat provided, including beef, chicken, and pork. They will refuse to eat if exposed to extreme temperatures.

Reproduction and lifespan[edit]

Maturity is reached at around 12 years of age.[20] Mating takes place yearly, in 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 two months later. The gender of the young 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.[21]

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 between 20 and 70 years.[22]

Under Human Care[edit]

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

Alligator snapping turtles are sometimes 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.[23]

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 is dangerous. Extreme temperatures 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 sides of the shell 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.[24] Some states where alligator snapping turtles do not naturally occur (such as California) prohibit them from being kept as pets by residents.

Turtle soup[edit]

Alligator turtles are used to make turtle soup.

Conservation status[edit]

Because of collection for the exotic pet trade, overharvesting for their meat, and habitat destruction, some states have imposed bans on collecting alligator snapping turtles from the wild, but they are not an endangered species.[25] 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 III species (which will put limits on exportation from the United States and all international trade in this species).[26]

The alligator snapping turtle is now endangered in several states, including Kentucky, Indiana, Illinois, and Missouri where they are protected by state law.[27][28]

In October 2013, one was found in the Prineville Reservoir in Oregon. It was captured and euthanized by the Oregon Department of Fish and Wildlife, which considers alligator snapping turtles to be an invasive species.[29] It was the first found in the state.

References[edit]

  1. ^ a b c Rhodin 2010, p. 000.92
  2. ^ Fritz 2007, p. 172
  3. ^ Fritz 2007, pp. 172–173
  4. ^ Carwardine, Mark (2008). Animal Records. Sterling Publishing Company, Inc. p. 174. 
  5. ^ "Biographies of People Honored in the Herpetological Nomenclature North America". Archived from the original on 10 July 2006. Retrieved 2006-07-09. 
  6. ^ 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. 
  7. ^ "Smithsonian National Zoological Park: Alligator Snapping Turtle". Archived from the original on 7 March 2006. 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. 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. 
  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. ^ a b c d e Pritchard, P. 1979. Encyclopedia of Turtles. Neptune, New Jersey: T.F.H. Publications, Inc.
  15. ^ http://news.ufl.edu/2014/04/10/alligator-snapping-turtles/
  16. ^ J. Howard Hutchison (2008). "History of fossil Chelydridae". In A.C. Styermark, M.S. Finkler, R.J. Brooks. Biology of the Snapping Turtle (Chelydra serpentina). Johns Hopkins University Press. pp. 14–30. 
  17. ^ a b c Ernst, C., R. Barbour, J. Lovich. 1994. Turtles of the United States and Canada. Washington, D.C.: Smithsonian Institution Press.
  18. ^ Elsey, R. 2006. Food Habits of Macrochelys temminckii (Alligator Snapping Turtle) From Arkansas and Louisiana. Southeastern Naturalist, 5: 443-452.
  19. ^ The Bronx Zoo: Alligator Snapping Turtle. bronxzoo.com
  20. ^ "Animal Diversity Web: Macrochelys temminickii". Retrieved 2008-09-12. 
  21. ^ "Nashville Zoo: Alligator Snapping Turtle". Archived from the original on 2006-02-21. Retrieved 2006-03-26. 
  22. ^ "WhoZoo: Alligator Snapping Turtle". Archived from the original on 28 April 2006. Retrieved 2006-03-26. 
  23. ^ AST Care Sheet. Austinsturtlepage.com. Retrieved on 2012-08-22.
  24. ^ "NAS — Species FactSheet". Retrieved 2006-03-26. 
  25. ^ "Alligator Snapping Turtle - National Wildlife Federation". Nwf.org. Retrieved 2013-04-22. 
  26. ^ "Alligator Snapping Turtle and Map Turtles Gain International Protection". Retrieved 2006-03-26. 
  27. ^ http://www.in.gov/nrc/files/Item_7_NRC_November_2010.pdf
  28. ^ "DNR". Dnr.state.il.us. Retrieved 2013-04-22. 
  29. ^ Thomas, Pete (October 23, 2013). "Prehistoric-looking alligator snapping turtle is not wanted in Oregon". GrindTV.com. Retrieved 2013-10-23. 


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