Northern map turtle (Graptemys geographica)
Like most turtle species, northern map turtle populations are in decline. Development projects have shrunk their habitats, while pollution in the areas that remain reduce the amount and quality of their food sources.
The northern map turtle gets its name from the markings on its shell, which resemble contour lines on a map. Males largely eat insects and crayfish, while females have powerful jaws that they use to crush molluscs, clams and snails. Female turtles may take more than 10 years to reach maturity and can grow to nearly twice as long as males. Northern map turtles breed in the spring and fall, with a nesting period lasting from May to July.
Northern map turtles live in lakes and large rivers with slow-moving water and a soft bottom. They need unpolluted water where females can find plenty of molluscs to feed on. Individuals from a wide area will often congregate at favoured sites to bask together. For nesting, they highly prefer unshaded sites with sandy, well-drained soil.
Northern map turtles inhabit an area from southern Quebec and Ontario to the St. Lawrence River drainage basin, extending west through the Great Lakes and into the central United States south to Oklahoma and Alabama. In southern Ontario, they are found primarily on the shores of Georgian Bay, Lake St. Clair, Lake Erie and Lake Ontario and along larger rivers including the Thames, Grand and Ottawa.
Water pollution poses a serious threat to northern map turtles, killing off the molluscs that female turtles depend on. In addition, invading zebra mussels in the Great Lakes region have crowded out native molluscs. Although northern map turtles will eat zebra mussels, they are not as palatable and likely not as rich in nutrients. Meanwhile, shoreline development contributes to habitat loss and degradation. Northern map turtles are also injured or killed by vehicle collisions on roadways and by boat propellers in the water. Nests are vulnerable to human-subsidized predators, such as raccoons, whose numbers are artificially inflated by access to human garbage, crops and other food sources.
Recommended Recovery Actions
The proposed national Management Plan calls for a number of conservation measures, including implementing techniques to control predators and increase hatchling survival and recruitment; reducing boating injuries and road mortality; conserving, managing and protecting habitat; and controlling the spread of invasive species.
What we are doing
Find out how Wildlife Preservation Canada helps save Canada’s reptiles and amphibians, including northern map turtles, and how you can make a difference.