Scientific name: Chelydra serpentina
Canada’s largest freshwater turtle, the Snapping Turtle, Chelydra serpentina, is monotypic for North America and globally is one of three species within the genus Chelydra and is one of four species within the family Chelydridae. The keeled carapace is brown, black or olive, and the cross-shaped plastron is much reduced compared with other turtles, leaving the limbs and sides of the body exposed. The Snapping Turtle’s head is large with a hooked upper jaw, the neck is relatively long, and the tail is approximately as long as the carapace. In a central Ontario population, adult males have an average carapace length of 32.3 cm and an average mass of 9.3 kg, whereas adult females average 28.5 cm carapace length with an average mass of 5.3 kg.
The Snapping Turtle has the greatest latitudinal distribution of any turtle in North America, ranging from southern Manitoba south to Texas, In Canada, the species is present in mainland Nova Scotia, southern New Brunswick, southern and central Quebec, southern and central Ontario, southern Manitoba and southeastern Saskatchewan. Within the Canadian range of the species, a range disjunction occurs in northwestern Ontario, north of Lake Superior. where summers are likely too cool for Snapping Turtle embryos to complete development successfully.
The preferred habitat for the Snapping Turtle is characterized by slow-moving water with a soft mud bottom and dense aquatic vegetation. Established populations are most often located in ponds, sloughs, shallow bays or river edges and slow streams, or areas combining several of these wetland habitats. Although individual turtles will persist in developed areas (e.g. golf course ponds, irrigation canals), it is unlikely that populations persist in such habitats. Snapping Turtles can occur in highly polluted waterways, but environmental contamination is known to limit reproductive success. Snapping Turtle habitat is diminishing in both quantity and quality in Canada with losses primarily due to conversion of wetlands to agriculture and urban development.
Snapping Turtles have a life-history strategy characterized by high and variable mortality of embryos and hatchlings, delayed sexual maturity, extended adult longevity, and iteroparity (repeated reproductive events) with low reproductive success per reproductive event. Females, and presumably also males, in more northern populations mature later (at 15-20 years) and at a larger size than in more southern populations (~12 years). Lifespan in the wild is poorly known, but long-term mark-recapture data from Algonquin Park suggest a maximum age of over 100 years. Nesting takes place in late May and June, with females laying approximately 40 eggs in a flask-shaped nest. In Algonquin Park, the probability of a Snapping Turtle embryo surviving to sexual maturity is less than 0.1%. Active adult Snapping Turtles have few predators other than humans, but in some localized cases, mammalian predators have developed techniques for preying upon hibernating adults.
Population sizes and trends
Although the Snapping Turtle is one of Canada’s more widespread turtle species, long-term studies of two populations in Ontario have demonstrated that even large and apparently secure populations are vulnerable to increases in adult mortality and do not recover quickly from declines. Life-history models indicate that only slight increases (0.1) in annual adult mortality rate (such as from road mortality or harvesting) will cause a population to be halved in under 20 years. The Snapping Turtle remains relatively abundant in eastern Canada, but is less often encountered in Saskatchewan and Manitoba.
Snapping Turtle populations in Canada are limited primarily by their life-history strategy (slow recruitment, late maturity, long lifespan, high adult survival) and by short, cool summers which reduce hatching success. Population persistence is critically dependent on high adult survivorship; thus, most of the serious threats to Snapping Turtles in Canada are events that increase adult mortality. Legal and illegal harvesting of adults, persecution and road mortality (particularly of females traveling to nest sites) are the most prominent causes of premature death in adult Snapping Turtles. Other long-term threats to the persistence of the Snapping Turtle in Canada include on going loss of habitat, decreased reproductive success due to environmental contamination, unnaturally high rates of nest predation by large populations of raccoons (Procyon lotor) and other mammals, boat propeller strikes, “bycatch” from both sport and commercial fishing, dredging, road grading, water drawdowns and other practices.
Special significance of the species
The Snapping Turtle is Canada’s largest terrestrial or freshwater reptile with a lifespan similar to or greater than humans and has scientific, ecological and cultural significance. Its prehistoric appearance is familiar to Canadians, many of whom have personal stories (often exaggerated) about the enormous size, jaw strength or ferocity of the species.
ourtesy Species at Risk Public Registry, Government of Canada