Northern Map Turtle
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| Graptemys geographica (Lestur, 1817) |
The Northern Map Turtle (Graptemys geographica) is an aquatic turtle belong to the family of Emydidae.
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[edit] Description
Northern Map Turtle gets their name from the marking of the carapace. The light markings resemble waterways on a map or chart. The lines on the carapace area shade of yellow or orange and are surrounded by dark borders. The rest of the carapace is olive or greyish brown. The makings on the older turtles may barely visible because of darker pigment. The carapace is broad with moderately low keel. The hind of the carapace is slightly scalloped shaped due to the scutes. The plastron of an adult map turtle tends to be plain yellowish color. The head, neck and limbs are dark olive, brown or black with thin yellow, green, or orangish stripes. There is also an oval spot located behind the eye of most specimens. There is sexual dimorphism in size and shape. The females are much larger than the males. The males also have a more oval carapace with more distinct keel, narrower head, longer front claws, and a long thicker tail. The males vent also opens beyond the edge of the carapace whereas the female's opens up the carapace. The young map turtles have a pronounced dorsal keel and patterns on the plastron consist of dark lines bordering the scutes. a hatchling has a rounded or grayish-brown carapace about 1 in long. The pattern is light circular markings. The stripes located on the head and limbs are just like the adults. Males are 3.5 inches to 6.5 inches long, while females are 7 to 10.5 inches long and its weight is around 1-5 pounds.
[edit] Distribution
Northern Map Turtle inhabits an area from south Quebec and northern Vermont where it lives in the St. Lawrence drainage. Its range extends west through the great lakes and into southern Wisconsin and eastern Minnesota, west of the Appalachians, south to Kansas, northwestern Georgia. It also occurs in the Susquehanna River system located in Pennsylvania and Maryland and also in the Delaware River.
[edit] Habitat
Northern Map Turtle inhabits ponds, river-bottoms, and lakes. The abundance of aquatic vegetation is preferred. They prefer large bodies of water and areas with fallen trees and other debris for basking.
[edit] Behavior
This turtle is dormant from November through early April. Most of that time is spent under the water, wedged beneath submerged logs, in the bottom of the mud of a lake or in a burrow. They have been known to change locations in the middle of the winter. They are avid baskers and they bask in groups. They are diurnal, active both in the day and at night. They are also a very wary animal; at the slightest hint of danger they slip into the water and hide. During courtship the male initiates by tapping his long claws on the front of the female but few details are known.
[edit] Reproduction
Northern Map Turtles breed in the spring and fall. Most mating makes place in deep waters. The nesting period lasts from May to July. Unshaded sites with sandy soil is highly preferred. The female usually chooses well-drained areas for depositing the eggs. The nest cavity is dug with the hind feet. The size of the clutch is between 6 to 20. The eggs are oval and have a flexible shell that is about 3.2 cm. After the eggs are laid the cavity is filled. They hatch between 50 to 70 days of incubation and most emerge in August to September. When a nest hatches late, the Northern Map Turtle has been known to overwinter in the nest. The female usually lays two or more clutches in one breeding season. The sexes of the young are determined by the temperature. 25 degrees C incubation will give the majority of males whereas 30-35 degrees C will yield more females.
[edit] Diet
This turtle is an omnivore. The feeding always takes place in the water. The adult female, due to their large heads and strong jaws eat larger prey than males. The females consume snails, clams, and crayfish. The males eat aquatic insects, snails, and smaller crustaceans. Both are known to eat dead fish and some plant material. As turtles become older however, up to 50% of their diet becomes plant based.
[edit] See also
[edit] References
- Conant, R.,J. Collins. 1998 Reptiles and Amphibians in the Eastern/Central North America. New York: Houghton Mifflin.
- Harding, J. 1997. Amphibians and Reptiles of the Great Lakes Region. Michigan: The University of Michigan Press.
