Alligator snapping turtle  (Macroclemys temminckii)

Amongst the largest freshwater turtles in the world, the alligator snapping turtle is a prehistoric-looking species with a reputation as the ‘dinosaur of the turtle world' (2). Its camouflaged, ridged upper shell (carapace), large head, powerful, hooked, beak-like jaws, thick, scaled skin and oversized claws all contribute to this species' primitive look and set it apart from other freshwater turtles (4) (5). The three large, pronounced ridges running down the length of the dark brown to blackish shell somewhat resemble those on the back of an alligator, and earn the species its common name (2) (6). The shell also often has algae growing on it, which adds to the snapping turtles' camouflage (6). The tail is almost as long as the shell itself and, together with the chin, throat and neck, is coated with long, pointed tubercles (7) (8). The alligator snapping turtle has an unusual way of luring prey to it; the tongue contains a small, pink, worm-like projection (lure), which is grey at rest but suffused with blood when active, and wriggled to attract prey into the turtle's mouth (2).

Endemic to the southeastern region of the U.S., occurring in the river system that drains into the Gulf of Mexico (1) (2) (9).

A freshwater species generally found in the deep water of large rivers, canals, lakes and swamps, though hatchlings and juveniles usually live in small streams (9). These turtles seldom leave the water, with generally only nesting females venturing onto land, although males have been known to bask (10).

The alligator snapping turtle is a solitary species, which mates in the early spring in Florida, later spring in the Mississippi Valley, and nests about 2 months later (8) (9). Nests are dug at least 50 m from the water's edge, into which a clutch containing anything between 8 and 52 eggs may be laid (9). Incubation lasts 100 to 140 days and most hatchlings emerge in September or October (8) (9). As with a number of reptiles, the sex of the young is determined by incubation temperature; high and low temperatures yield more females and moderate temperatures yield more males. Sexual maturity is attained between 11 and 13 years of age, and alligator snapping turtles have been known to live up to 70 years in captivity, although the lifespan in the wild is unknown (11).

The alligator snapping turtle actively forages for food at night, but is more of a sit and wait predator during the day. The turtle lies quietly on the mud bottom with its jaws wide open, the dark colouring of its mouth-lining and exterior, which is coated in algae, making it almost invisible to fish (9). The worm-like lure within the turtle's mouth is wiggled to entice unwary fish and, when the unlucky fish comes close, the turtle's jaws are quickly snapped shut (6) (9). The alligator snapping turtle not only feeds on a variety of fish, but also on frogs, snakes, snails, worms, clams, crayfish, aquatic plants and even other turtles (9).

A major decline in numbers occurred as a result of over-collection by one of the major soup manufacturing companies in the U.S., and alligator snapping turtles are still threatened by over-harvesting for their meat in many areas of the U.S. (8) (12). Although some states now prohibit collection of this species, other states allow it with permits (13). Other threats to this turtle include habitat destruction and alteration, water pollution and pesticide accumulation (1) (9) (13).

Collecting wild specimens is prohibited in Arkansas, Florida, Georgia, Indiana, Missouri, Tennessee, but allowed with the necessary permit in Alabama, Illinois, Kansas, Louisiana, Oklahoma and Texas. The alligator snapping turtle has been found in reservoirs throughout its range, and dyking of rivers to create winter waterfowl refuges has increased the available habitat in Arkansas and the lower Mississippi Valley, which may help offset some of the habitat degradation and loss seen elsewhere (1).

For more information on the alligator snapping turtle see:

• Alligator Snapping Turtle Foundation:
  http://www.astfoundation.org
• The Centre for Reptile and Amphibian Conservation and Management:
  http://herpcenter.ipfw.edu/
• Turtles of the World (CD-ROM), by Ernst, C.H., Altenburg, R.G.M. and Barbour, R.W.:
  http://nlbif.eti.uva.nl/bis/turtles.php?selected=beschrijving&menuentry=soorten&id=189

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