What Is It Wednesday: Northern Map Turtle

Name: Northern Map Turtle (Graptemys geographica) 

The Northern Map Turtle is one of eight native turtle species found in Ontario. Its name is derived from the map-like contour lines that run along the top of its shell, also known as the carapace, and the bright, yellow lined pattern on its skin. Its lower shell, or plastron, is usually a light yellow to cream and behind its eyes, this turtle sports a bright, yellow spot.

(Photo Credit: Scott Gillingwater)

Unlike most of its freshwater turtle counterparts, the females and males of this species differ in size and diet. Females have been known to grow larger than 25 cm, almost doubling the average size of the males at 14 cm. Although both enjoy dining on crayfish, males are more partial to insects and females prefer a variety of molluscs, such as clams and snails, as well as some fish. Females also take a lot longer to mature than males; it can take upwards of 10 years for a female, but a male may reach maturity after about 4 years. Nesting takes place from June to July, where 10-22 elliptical shaped eggs will be deposited and buried until the hatchlings emerge sometime in the fall.

In Ontario, this turtle haunts the shores of lakes and rivers, including Georgian Bay, Lake St. Clair, Lake Erie, Lake Ontario, the Thames River, Grand River, and Ottawa River (Figure 1). Habitat must include high-quality water and acceptable basking sites to support the mollusc diet of the females and to enable lots of sun-loving moments for basking. For this species, basking can take place on rocks and logs, but they will also bask just under the water’s surface with only their head or nose exposed. (Photo Credit: Dave Wavell)

Federally and provincially, Northern Map Turtles are considered Special Concern species meaning there is potential for the species to become endangered or threatened based on its biological characteristics and known threats to the species. Primary threats include habitat loss and destruction, poor water quality, roadway and motorboat mortality, the spread of invasive species like Zebra Mussels, and illegal pet trade capture and exporting. This species and its habitat are offered no protection under the Endangered Species Act, although collection and ownership is prohibited by the Fish and Wildlife Conservation Act.

You can help to protect this species by reporting any sightings to the National Heritage Information Centre (NHIC), volunteering with local conservation groups to do turtle surveys and stewardship work, and reporting illegal activities.

Fun Fact: Northern Map Turtles are communal sunbathers. It is not unusual to see up to 30 turtles piled on top of each other, soaking up the sun together.

Figure 1: Northern Map Turtle range map for Ontario (https://www.ontario.ca/page/northern-map-turtle).