Graptemys geographica

Description

The northern map turtle gets its name from the markings on its carapace – yellow, tan or orange markings surrounded by dark borders resemble contour lines on a map.  The rest of the carapace is olive or grayish brown and has a distinct ridge along the centre and serrations along its back edge. Both the head and legs have an intricate pattern of bright yellow lines. Northern map turtles have a yellow spot behind the eyes.  Males are 10-16 cm in length and weigh between 150-400 g while females are larger at 18-27 cm with a weight of 0.5-2.5 kg.  Males largely eat aquatic invertebrates while females have powerful jaws that they use to crush molluscs with.  Female turtles may take more than 10 years to reach maturity.  Northern map turtles breed in the spring and fall with a nesting period lasting from May to July.  The size of the clutch is between 6 and 20.

Habitat

Northern map turtles inhabit large rivers and lakes with slow-moving water and a soft bottom. They require high water quality that supports the female’s mollusc prey.  Individuals from a wide area will often congregate at favoured sites to bask together.  Unshaded sites with sandy soil are highly preferred for nesting, where the female usually chooses well-drained areas for depositing the eggs.

Distribution and Population Size

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.  Like most turtles, northern map turtle populations are in decline.  In Canada, this species has been listed as special concern by the Committee on the Status of Endangered Wildlife in Canada.

Threats to Survival

Water pollution poses a serious threat to northern map turtles, causing die-offs of the molluscs on which female turtles depend.  In addition, the invasion of zebra mussels into the Great Lakes region has caused declines in traditional prey species, and while they will eat zebra mussels, it is not a preferred food source and likely not as nutient-rich.  Habitat loss and degradation due to shoreline development are additional threats to this species.  Northern map turtles are also vulnerable to vehicle collisions on roadways and propeller injury and death in the water.

What you can do to help

• Make a contribution today towards WPC’s Freshwater Turtle recovery activities.

• Every year, turtles must cross busy roads to get to their nesting sites – watch for turtles on the roads, especially between May and October.

• Never buy native species of turtles or any turtles that have been caught in the wild.

• Don’t disturb nests, young or adults – be respectful and observe from a distance.

• Help reverse the loss of turtle habitat by protecting or restoring wetlands and surrounding vegetation on your property.

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