Common Snapping Turtle (Chelydra serpentina)

Distribution: The range of the common snapping turtle extends from Nova Scotia, New Brunswick, and southern Quebec west to southeastern Alberta, and southward east of the Rocky Mountains to southern Florida and the Texas coast in the United States.

Habitat: Typically found in almost every kind of freshwater habitat, but prefers slow-moving water with a soft mud or sand bottom and abundant aquatic vegetation. Generally lives in shallow bodies of water, but may live along the edges of deep lakes and rivers. Florida snapping turtles are frequently found in canals, sloughs, and pools and can be found in acidic, muck-bottom hammock streams. The snapping turtle may also enter brackish coastal waterways (Kiviat 1980).

Behavior: Chelydra usually moves slowly over the bottom; however, if disturbed it can swim rapidly. It usually spends the bulk of the day floating just beneath the surface, lying on the bottom of a deep pool, or buried in the mud in shallow water. A social relationship with Chrysemys picta (painted turtles) basking on the back of a floating snapping turtle has been described by Legler (1956). In the southern range, the turtle may be active year round. In the northern range, hibernation begins by late October; however, radiotelemetry studies indicate not all snapping turtles hibernate (Ultsch and Lee 1983). Burrowing in mud bottoms, or using muskrat burrows or lodges is the typical overwintering preference. Large congregations sometimes hibernate together (Meeks and Ultsch 1990). Emergence from hibernation usually occurs in April or as late as May in Canada. While basking can occur out of water, it occurs most frequently in the water with the turtle floating on the surface with just the head and top of the carapace exposed. Aerial basking is restricted by the animal's intolerance of high temperatures and by rapid loss of moisture. Hatchlings are attracted to large areas of intense illumination, which allows them to find their way from the nest to the water.

Reproduction: Mating occurs from April to November with peak nesting from 15 May to 15 June; however, nesting may occur prior to this in the south or afterwards in the north (Ewert 1976). Nesting in Canada may not begin until mid-June, with the season extending into July (Robinson and Bider 1988). The nesting cycle is bimodal (morning and evening) over most of its range, (e.g. New York, Michigan); however, this is not true for all locations (e.g. Virginia, mostly morning nesting) (Petokas and Alexander 1980). Nests are dug with the hind feet in an open site in relatively loose sand, loam, vegetable debris, or sawdust piles. Muskrat and beaver lodges are sometimes used, as well as manmade sites such as roadsides, railways, and dams. Clutch size is variable, ranging from 6 to 104 (typical range: 20-40). Incubation time, longest in the northern region, ranges from 55 to 125 days, but 75 to 95 days is more typical (Congdon et al. 1987). Emergence from the nest normally occurs from mid-August to early October, but may be earlier in the southern range or delayed until the following spring (southeastern Pennsylvania; Ernst (1966)). More northern populations in the United States and Canada have very low frequencies of overwintering in the nest by hatchlings (Obbard and Brooks 1981). Gender determination is temperature-dependent.

Food habits: Common snapping turtles are omnivorous, eating almost anything to include insects, spiders, isopods, amphipods, crayfish, fiddler crabs, shrimp, clams, snails, earthworms, leeches, freshwater sponges, frogs and toads, salamanders, small turtles, snakes, fish, aquatic or semiaquatic birds, plant material, and small mammals. The snapping turtle is considered a nuisance since it consumes game fish and ducklings (Abel 1992).

Populations: Even though snapping turtles are among the more abundant aquatic turtles, overcollecting has seriously reduced many populations (Ernst et al. 1994). Studies have shown sex ratios within a population are typically 1:1 and this ratio is maintained throughout adulthood (Mosimann and Bider 1960). After emergence from the nest, hatchlings and juvenile size and age classes may predominate in the population; however, this is short-lived due to their high mortality. Chemical pollution is linked to population decline (Ryan et al. 1986).