This is the largest freshwater turtle in North America and is among the heaviest freshwater turtles in the world. Though once found in the depths of southern Indiana's largest rivers, they are now likely extirpated in Indiana. These turtles are almost wholly aquatic and any turtle found moving over land is almost certainly not this species. Alligator Snapping Turtles have large heads and jaws, a long spiny tail, and a broad carapace with three raised, parallel ridges. Large adults may grow to over 150 lbs with shells up to 25 in (60 cm) across.
Upon encountering a large Snapping Turtle, many people believe they have found an Alligator Snapping Turtle. However, in Indiana, Alligator Snapping Turtles are extremely rare and may now be extirpated. Snapping Turtles may grow up to 70 lbs and have a similar long tail, sharp-serrated rear scutes on the shell, and large heads. Other than the notable size difference in large adults, the three raised ridges on the shell of an Alligator Snapping Turtle are also useful in differentiating the two. Perhaps most notably, Alligator Snapping Turtles are almost entirely aquatic and rarely (if ever) move over land. Snapping Turtles, on the other hand, frequently make long-distance movements over land and are often encountered crossing roads.
Ecology and Conservation
Alligator Snapping Turtles are massive and have been documented as weighing in at well over 200 pounds, with a shell length of 79cm (31 in) and heads as large as 24 cm (9.5 in)! They are highly aquatic and prefer large slow-flowing streams or tributaries with large holes and mud at the bottom. They can also be found in canals, lakes, oxbows, swamps, ponds and bayous.
Alligator Snapping Turtles are threatened by overharvesting for food in many areas. In the Midwest, the Alligator Snapping Turtle is State Endangered in Indiana and Illinois. This species is considered imperiled in Missouri.
Alligator Snapping Turtles are known from the lower Wabash and Ohio Rivers from historic written and oral accounts as well as old, bleached shells and shell fragments found in the area. They may have been more widespread at one time, but presumed sharp population declines coupled with the scarcity of incidental encounters with such an aquatic animal make understanding their historic population trends impossible. A more recent record for a large adult in the White River likely represent either an escaped/released captive animal or a very old adult that gradually made its way upstream from populations further south. In all likelihood, this species is either extirpated or functionally extirpated (no breeding population, just a few old adults) in rivers in Indiana. The species is also found in Iowa.
While there is some debate as to the species-level taxonomy of the Alligator Snapping Turtles, individuals in Indiana belong to the species M. temminckii in all proposed taxonomic arrangements. Alligator Snapping Turtles belong to the family Chelydridae, which is represented by a total of two species in Indiana.
Conant, R. and J. T. Collins. 1998. A Field Guide to the Reptiles and Amphibians: Eastern and Central North America. Houghton Mifflin Company, New York, NY.
Ernst. C. H., J. E. Lovich and R. W. Barbour. 1994. Turtles of the United States and Canada. Smithsonian Institution Press, USA.
Harding, J. H. 1997. Amphibians and Reptiles of the Great Lakes Region. The University of Michigan Press. Ann Arbor, MI.
Minton, S. A. 2001. Amphibians and Reptiles of Indiana. Indiana Academy of Science.