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Description
This large turtle can reach up to 27 cm
carapace length. The carapace is
oval with a distinct low
keel and serrations
along the back edge. It is olive green in colour with a pattern of fine yellow lines on the
carapace, vaguely resembling a map. Both the head and legs have an intricate pattern of bright
yellow lines. The plastron is
cream to yellow in adults but in
juveniles there
are dark lines along the seams.
Confusing Species
Painted Turtles have similar colouring on the head
and neck but also have red markings on the margin of the carapace and lack both the serrations
and keel.
Blanding's Turtles have yellow markings on the
carapace but lack the serrations, and keel, as well as the marking on the head.
Distribution
In Canada, Northern Map Turtles are found in southern Ontario, east along the St. Lawrence
River and into Québec. They range through the central United States south to Oklahoma
and Alabama.
Habitat
Northern Map Turtles inhabit larger rivers and lakes with slow moving water and a soft bottom.
They require high quality water which supports their mollusc prey. Individuals may congregate
in areas with abundant basking sites.
Reproduction
Females may require more than 10 years to reach maturity. Nesting occurs from June through
July. A single clutch of up to 17 eggs is laid. Hatching occurs in fall although in cool years
eggs may not hatch at all. It is possible that in some cases hatchlings overwinter in the
nest. The gender of hatchlings is determined by incubation temperature of the eggs.
Natural History
Northern Map Turtles are known for their communal basking and many individuals may be found
piled up together. Basking is particularly important for females prior to egg laying and in
the fall prior to hibernation. Northern Map Turtles have very strong jaws and specialize in
eating molluscs such as snails and clams although crayfish, other invertebrates and even some
fish are also eaten. Individuals can live more than 20 years.
Conservation Concerns
Populations may be large, however they are vulnerable to water pollution which reduces mollusc
populations. In addition, shoreline development destroys nesting habitat. Adult females are
also vulnerable to traffic mortality as they wander in search of nest sites. The Northern Map
Turtle has been designated Special Concern in Canada by
COSEWIC
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