The alligator snapping turtle is the largest freshwater turtle in North America. Male alligator snapping turtles can reach lengths of 29 inches (73.7 centimeters) and 249 pounds (112.9 kilograms), while females can reach lengths of 22 inches (55.9 centimeters) and 62 pounds (28.1 kilograms) (Ewert et al. 2006, Pritchard 2006). The inner mouth lining is gray/brown with black splotches, which is different from most turtles; others have a pink lining (Ewert et al. 2006). This species also has a tremendously long tail; large, triangle-shaped head; curved beak; and a rough brown shell with three spines that run vertically up the shell (Florida Natural Areas Inventory 2001).
The alligator snapping turtle can be found in rivers, lakes, backwater swamps, and periodically in brackish water systems (mixture of fresh and salt water) from Florida to Texas and north to Illinois (Florida Natural Areas Inventory 2001). In Florida, this species can be found in the Panhandle and Big Bend regions, from the Escambia River east to the Suwannee River (Ewert et al. 2006, Pritchard 2006, Map Data from: Krysko et al. 2011).
The Alligator Snapping Turtle: Biology And Conservation
Alligator snapping turtles were historically used as food in their southern range; the highest amount of harvesting occurred in the 1960s and 1970s, which caused regional population declines (Reed et al. 2002). Mortality rates slowed in the 1970s in Florida when the Florida Game and Fresh Water Fish Commission (now the Florida Fish and Wildlife Conservation Commission) enacted rules to limit the take of alligator snapping turtles. Presently, under Rule 68A-27.005 of the Florida Administrative Code, it is illegal to take, possess, or sell the alligator snapping turtle, as it is a protected species. It could take decades for the alligator snapping turtle to recover from the pre-1970 overharvesting. Bycatch (organisms caught in fish nets that are not wanted) mortality on lines set for fish, especially catfish, is a present threat to the alligator snapping turtle. Included in these lines are both trot lines (long lines of submerged baited hooks) and bush lines (single hooks suspended from tree branches) (Ewert et al. 2006, Pritchard 2006). Chemical pollution from industry and farms are a threat to all riverine species, even though a spill in one river would not endanger the species statewide (Ewert et al. 2006). Siltation from road crossings could potentially reduce the quality of smaller streams utilized by this species, such as the clear seepage streams on Eglin Air Force Base. Natural threats include the possible increased predation on their eggs from raccoons, wild hogs, and red imported fire ants.
Ewert, M. A., and D. R. Jackson. 1994. Nesting ecology of the alligator snapping turtle (Macroclemys temminckii) along the lower Apalachicola River, Florida. Florida Game and Freshwater Fish Commission, Nongame Wildlife Program Report NC89-020, Tallahassee, Florida. 45pp.
Reed, R. N., J. D. Congdon, and J. W. Gibbons. 2002. The alligator snapping turtle (Macroclemys [Macrochelys) temminckii]: a review of ecology, life history, and Alligator Snapping Turtle Biological Status Review Report 8)
Among the largest freshwater turtle species in the world, alligator snapping turtles may obtain weights over 100 kg (220 lbs) and carapace lengths up to 80 cm (31 inches). The carapace is broad and relatively flat and bears three jagged ridges along its length, prominent in all but the oldest of individuals. In addition, the presence of 1-5 (usually 2-3 in individuals) supramarginal scutes is unique to this turtle. The carapace is dark-brown to reddish-brown and patternless. The similarly colored plastron is very reduced and cross-shaped. The enormous head, which has earned it the nickname "loggerhead," is triangular in shape and has an elongated snout with strongly hooked jaws. The skin is typically dark brown in color, but some individuals may be flesh-colored. Many small dermal projections are present on the chin and neck. The relatively long tail has three dorsal rows of tubercles. Two species of alligator snapping turtles occur in Georgia, with the Suwannee Alligator Snapping Turtle being restricted to waters of the Suwannee River drainage, and the nominate species occurring in other Gulf of Mexico drainages. Morphologically, the two species can only be distinguished based on subtle differences of certain scutes on the carapace, and by the shape and arrangement of particular bones in the skull.
Common snapping turtles (Chelydra serpentina) are similar in color and general appearance but have less conspicuous carapace ridges, a much smaller head with no elongation of the snout, lack supramarginal scutes, and have a jagged keel on the tail. Further, common snappers are frequently seen on land while alligator snappers almost never leave the water except to nest.
Mating takes place in late winter or early spring and is subsequently followed by an April through June nesting season. Nests are usually dug in riverbanks, where 10-61 round, leathery eggs are deposited. Females are capable of producing only one clutch each year and some may nest only every other year. Hatchlings, whose gender is determined by the incubation temperature of the eggs, emerge 2 -3 months following nesting. Sexual maturity is reached in approximately 11-13 years. Alligator snapping turtles, especially younger individuals, are known for the unusual feeding behavior of lying otherwise motionless on the stream bottom with their jaws agape, wiggling their specialized, worm-like tongue appendage. This action lures small, unsuspecting fish within range of their lightning-quick and extremely powerful jaws. Thought to be relatively sedentary by some, alligator snapping turtles have been documented moving considerable distances upstream.
Prior to receiving protection in the state, these giants were trapped heavily for commercial purposes, particularly to supply meat for the turtle soup industry. One individual trapper was responsible for harvesting between 4,000 and 5,000 adult alligator snapping turtles from the during the period 1971-1983. This individual also reported catching up to 450 kg (1,000 lbs) of this turtle per day in one of the Flint River's tributaries. Removing this many adult turtles, especially of a late maturing species like the alligator snapping turtle, can seriously impact a local population. This was substantiated after a 1988-1989 survey of the conducted by the aforementioned trapper yielded only 62 alligator snappers in 783 trap nights. Many turtles also die after becoming hooked or ensnared on abandoned bush hooks and trotlines. In and some European countries, they are still sought out as pets as well as for food. Water pollution and stream dredging have also been implicated as threats to this species.
Conducting research to aid the conservation of a species whose numbers have declined is often challenging precisely because they are scarce. For animals that are naturally secretive, they are even more difficult to detect and therefore study. One such species is the alligator snapping turtle which after decades of population decline has been petitioned for federal listing as an endangered species three times. These large turtles are of particular interest to Dr. Day Ligon, associate professor of biology at Missouri State.
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Conservation of coastal rivers of the northern Gulf of Mexico is vital to the survival of the alligator snapping turtle, including two recently discovered species, University of Florida scientists say.
A new study appearing this week in the journal Zootaxa shows the alligator snapping turtle, the largest freshwater turtle in the Western Hemisphere and previously believed to be one species, is actually three separate species.
Kessler and his collaborators tested how well an emerging environmental sampling technique known as environmental DNA, or eDNA, could detect alligator snapping turtles in a southern Illinois river system. The idea is that all organisms shed DNA in the environment as they go about their daily business. Therefore, a simple scoop of soil or water should theoretically contain trace amounts of DNA from all the organisms recently inhabiting or passing through a given area.
The eDNA method was able to detect alligator snapping turtles up to a kilometer, or two-thirds of a mile, downstream. Remarkable, considering less than a gallon of water was taken from each sampling location.
Starting in 1999, scientists at the hatchery brought the animals on station and developed captive-breeding and -rearing techniques, with much success. While they have not abandoned their work with paddlefish, catfish, and the endangered Arkansas River shiner, the alligator snapping turtle has risen in importance if for anything but to stave off a potential listing under the Endangered Species Act. You might say they are getting out in front of the emerging conservation issues.
Alligator snapping turtles from Tishomingo were tagged, stocked in the Caney River and Pond Creek in northeastern Oklahoma, and later re-caught. Some of the 246 tagged turtles were never seen again. Others were caught multiple times for several years in the nets baited with dead fish set out in the late afternoons. When those turtles were re-captured, scientists measured their size and weight. Those data were compared to the same age of alligator snapping turtles that were kept at the Tishomingo National Fish Hatchery over the same period, revealing that the wild-raised turtles put on more mass and size than did those kept in captivity. 2ff7e9595c
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