Chelydra serpentina (Linnaeus, 1758)
Common Snapping Turtle
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Basis for Listing
The common snapping turtle occurs throughout the eastern United States and southern Canada. It is found in a wide variety of aquatic habitats throughout Minnesota (not reflected on range map). Despite its widespread occurrence, several factors prompted concern for the snapping turtle's status in Minnesota and led to its listing as a special concern species in 1984. The major factor is the unknown and possibly detrimental effects of commercial harvest on local populations. Common snapping turtles are harvested for their meat, and used for human consumption. The Minnesota DNR allows licensees to take an unlimited number of adults, provided that the carapace length is greater than 30.5 cm (12 in.). Complicating the situation is the fact that peak harvest often occurs in June, which coincides with annual egg-laying activities. Because females are long-lived and reproduce for 5-10 years (sometimes longer) once they obtain a minimum carapace length of 25 cm (10 in.), there is the potential that intense harvesting may significantly affect local breeding populations. Harvest figures are also high in early spring and late autumn when common snapping turtles are together in communal hibernacula. These areas are susceptible to over-trapping.
The common snapping turtle is Minnesota's largest turtle. As an adult, its upper shell (carapace) averages 20-36 cm (8-14 in.) in length and its weight ranges from 4.5-16 kg (10-35 lbs.). The largest known Minnesota individual weighed 29.5 kg (65 lbs.) and had a carapace that was 49.5 cm (19.5 in.) long. The common snapping turtle's carapace is variably colored from green to brown to black, and often has moss covering it. In young turtles, raised crests form three longitudinal keels along the carapace. These crests gradually disappear as the turtles mature. The back edge of the carapace in all sized turtles is strongly toothed. The lower shell (plastron) is considerably reduced in size relative to the upper shell, and provides little protection for the turtle. Common snapping turtles have a long tail with a series of raised scales along the top that create sawtooth projections. Their head is large, with large, powerful jaws, and their neck is long. The common snapping turtle is usually docile in the water, but can be aggressive when it is on land, often lunging forward and striking out to "snap" at its foe.
Common snapping turtles occur in virtually all aquatic habitats throughout the state, but prefer slow-moving, quiet waters with muddy bottoms and dense vegetation. They are common and often abundant in lakes, rivers, and marshes.
Biology / Life History
The common snapping turtle is a permanent resident of Minnesota which overwinters from October to late April. They overwinter in shallow water, and may either sit on the bottom, or shelter themselves by digging into the mud or staying under debris or overhanging banks. Many common snapping turtles may congregate in one area to overwinter. Breeding takes place any time that the turtles are active, but occurs most frequently in the spring and fall. During June, females travel to open areas that are suitable for nesting, and may travel 1 km (0.62 mi.) or more from water. Suitable nesting areas must be open and sunny and contain moist but well-drained sand or soil. Nesting areas are commonly sandy banks and fields, but also include gravel roads and lawns. The female uses her hind feet to dig out a cavity, and then lays 10-100 (usually 25-50) eggs, using her hind feet to guide them into the nest. The eggs are 2.2-3.2 cm (.87-1.25 in.) in diameter, white, and have a leathery shell. Once the eggs are laid, the female covers the nest with sand or soil and returns to water. Depending on the weather, the eggs will hatch in 50-125 days. Incubation temperature affects the sex of the hatchling turtles, with more females hatching during warmer temperatures, and more males hatching during cooler temperatures. Hatchling turtles use their egg tooth and claws to break out of their shell, and then must dig their way out of the nest and find water. When they emerge, hatchlings are 2.5-3.2 cm (1-1.25 in.) in length. Young turtles are vulnerable to predation and desiccation. From any given clutch of eggs, 60%-100% of the young may be lost to predators. Primary nest predators include raccoons (Procyon lotor), skunks, foxes, and mink (Mustela vison). In addition to these animals, hatchlings are also preyed on by large fish, large frogs, northern water snakes (Nerodia sipedon), and some bird species. Common snapping turtles are slow to mature, reaching sexual maturity in 5-7 years.
Conservation / Management
Common snapping turtles are sometimes blamed for a reduction in fish and waterfowl populations. Studies have shown, however, that common snapping turtles eat insignificant amounts of game fish, and that mammalian nest predators and large fish kill far more waterfowl than do common snapping turtles. As adults, common snapping turtles have few predators other than humans. Serious concerns have been raised about the effect of harvesting on common snapping turtle populations. An analysis of harvest patterns is needed to assess the impact on local populations. Additionally, common snapping turtles can store contaminants in their body fat, liver, muscle tissue, and eggs. The effect of these contaminats on the turtles' reproductive capacity is unknown and warrants further study.
Conservation Efforts in Minnesota
A 2001 study of turtles in the Weaver Bottoms area of the Upper Mississippi River found reduced numbers of common snapping turtles and suggested that harvesting and unintended drowning by commercial fisherman might be responsible (Pappas et al. 2001). Subsequently, updates to Minnesota's commercial turtle harvesting rules were made and implemented in 2004. These changes included limiting the number of traps which could be used, restricting turtle licenses to Minnesota residents, and putting a moratorium on the sale of new licenses. Anyone who held a license prior to the rule changes was permitted to renew it and they may pass their license down one generation to their relatives. Additionally, trappers must now keep a daily log of where their traps are located and how many turtles they harvest. These logs must be submitted monthly during the trapping season (March - November). Failure to submit this report to the Minnesota DNR can result in nonrenewal of a harvester's license. The DNR created a database in 2004 to maintain the trapping data, which will allow for greater monitoring of common snapping turtle harvest and population levels in Minnesota.
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