Northern map turtle © Joe Crowley
The northern map turtle (Graptemys geographica) is named for the markings on its shell, which look like the contour lines on a topographical map. The carapace (upper shell) is olive green with fine yellow lines and has a distinct ridge (keel) along the centre and serrations along its back edge. Both the head and legs have an intricate pattern of bright yellow lines. This turtle has a yellow spot behind the eyes. The plastron (lower shell) is cream to yellow in adults, but in juveniles the plastron has dark lines along the seams. Females get much larger than males and grow up to 27 centimetres in carapace length, whereas males grow to only 13 centimetres long.
Painted turtles have similar colouring on the head and neck, but their carapace has red markings along the sides and lacks the keel down the centre and the serrations along the back edge. Young Blanding’s turtles can have yellow markings on the carapace but also have a distinct yellow chin and throat, as well as a very domed shell. Snapping turtles get significantly larger than map turtles and have prominent ridges on their tail and lack the patterning on the shell and bright yellow lines on the face and legs.
Northern map turtles inhabit large rivers and lakes with slow-moving water and a soft bottom. They require high-quality water that supports the female’s mollusc prey. These turtles may congregate in areas with abundant basking sites.
View an interactive map of the known ranges of northern map turtles in Ontario.
Female northern map turtles may take more than 10 years to reach maturity. They nest from June through July and lay a single clutch of up to 17 eggs. They hatch in the fall, and in some cases the hatchlings overwinter in the nest. The incubation temperature of the eggs determines the gender of the hatchlings.
Northern map turtles are known for their communal basking, and many individuals may be found piled up together. This species has very strong jaws. The large females eat molluscs such as snails and clams, as well as crayfish, other invertebrates and some fish. Males and juveniles eat insects and crayfish. Individuals of this species can live more than 20 years.
Other names: common map turtle, Malacoclemmys geographica, Testudo geographica
Threats and Trends
Although many populations of northern map turtles in Ontario are large, water pollution poses a serious threat because it can cause mass die-offs of molluscs, the primary food of female map turtles. Habitat loss and degradation due to shoreline development are additional threats to this species. It is also vulnerable to mortality on roadways, and a recent study documented high rates of injury from boat propellers.
Current Status and Protection
The northern map turtle is currently listed as Special Concern under the Ontario Endangered Species Act, 2007 and Special Concern under the federal Species at Risk Act. The species has also been designated as a Specially Protected Reptile under the Ontario Fish and Wildlife Conservation Act. These acts offer protection to individuals and their habitat. The habitat of this species is further protected in Ontario by the Provincial Policy Statement under the Planning Act. The International Union for Conservation of Nature has not assessed the global status of the northern map turtle. The species’ status was confirmed in January 2010. Additional detail about legal protection for species at risk in Ontario is available on our Legal Protection page.
Learn more about reptile and amphibian conservation and what you can do to help these species on our Reptile and Amphibian Stewardship page.