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Canadian Herpetological Society Société d'Herpétologie du Canada |
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Snapping Turtle
Chelydra serpentina
Family: Chelydridae
COSEWIC status:- Special Concern
- Special Concern
- Least Concern
Description
Snapping Turtles have a relatively flat carapace (upper shell) that is typically brown, olive or black with a serrated rear edge. There are three low keels along the carapace but the keels become less obvious with age and older adults are relatively smooth-shelled. The carapace can often have algae growing on it, especially near the rear. The plastron (lower shell) is yellow to tan and reduced in size, giving it a cross-shaped appearance. The skin colour is generally grey to black, but the limbs and tail have a tan underside. Elevated scales (“spikes”) run along the tail, which is roughly as long as the carapace. The feet are webbed and have large claws. Snapping Turtles can reach a maximum carapace length of 49 cm, making them Canada’s largest freshwater turtle species. Hatchlings have a carapace length of 2–4 cm and resemble the adults.
Similar Species
With its massive head, large legs, and long, serrated tail, the Snapping Turtle has a unique “dinosaur-like” appearance. Juvenile Snapping Turtles can be confused with Eastern Musk Turtles, but Eastern Musk Turtles have a more domed carapace, a larger plastron, and a shorter tail.
Distribution
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The Snapping Turtle is widespread in Canada from southern Saskatchewan to Nova Scotia. It occurs across the central and eastern United States from Montana and New Mexico west to the Atlantic Coast.
Habitat
Snapping Turtles make use of an extremely wide range of aquatic habitats, but seem to prefer slow-moving waterways with a soft mud or sand bottom and abundant aquatic vegetation. Occupied water bodies are typically shallow, but Snapping Turtles can also be found along the edges of deep lakes. Typical water bodies used by Snapping Turtles include fens, bogs, swamps, marshes, permanent or temporary ponds, and shallow bays of lakes and rivers. Individuals overwinter in the soft bottoms of these water bodies. Females nest in open-canopy habitats with high sun exposure, such as in forest clearings, meadows, shorelines, rock outcrops, agricultural fields and the shoulders of roads. The nest sites are typically within a few hundred metres of a wetland or water body.
Biology
In Canada, Snapping Turtles are dormant during the winter and are active from late March or April until late September or October, depending on latitude. Females nest in late May or June and may travel several kilometers to reach their nesting site, often moving extensive distances overland through forests, fields and other terrestrial habitats. The female excavates a nest cavity in soil, sand or gravel substrate and typically deposits 25–45 round eggs, but some females have been reported to lay over 100 eggs. Hatchlings typically emerge in late August or September and their sex depends on the incubation temperature of the eggs; females are produced at temperatures below 21°C and above 28°C and males are produced at intermediate temperatures. Snapping Turtles do not reach sexual maturity until 17–19 years of age, and most females breed every year once they reach maturity. Snapping Turtles are very long-lived, and individuals can reach over 70 years of age. Snapping Turtles are omnivorous and will eat almost anything they can catch, including invertebrates, fish, frogs, plant material and carrion. Snapping Turtles bask out of the water less often than many other species of turtles. Home ranges vary greatly in size from 1–8 ha. Males regularly engage in combat over territory or females and these skirmishes can sometimes lead to severe injuries.
Threats
The extensive loss of wetlands is a threat across the range of the Snapping Turtle, although wetland loss has been most severe in the southern portion of their Canadian range. Individuals are especially susceptible to mortality on roads due to the long-distance terrestrial movements that are common to this species, as well as the tendency for females to nest on gravel roads or road shoulders. Since adult Snapping Turtles normally have an extremely long lifespan, the additional loss of only a few adults a year can cause population declines. Nest predation by subsidized predators (e.g. Raccoon, Skunk) can be a serious threat in areas where these nest predators are hyper-abundant. Harvest of Snapping Turtles for human consumption may also threaten some populations, particularly in Ontario where this activity is still legal. Many people fear Snapping Turtles due to the widespread misconception that they are dangerous to swimmers, while others dislike this species because they may prey upon waterfowl or fish. As a result, Snapping Turtles are often killed when encountered by humans. Other threats include introduction of exotic invasive species, mortality and injury from fishing by-catch, and chemical contamination of aquatic habitats. Climate change poses a potentially serious future threat to Canadian turtles.