Length: females are 7 to 10.5 inches and males are 3.5 to 6.5 inches.
Common map turtles get their name from the markings on the carapace. The light markings resemble waterways on a map or chart (Conant and Collins 1998). The lines on the carapace are a shade of yellow or orange and are surrounded by dark borders. The rest of the carapace is olive or grayish brown. The markings on the older turtles may be 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 (Harding 1997). The plastron of an adult map turtle tends to be plain yellowish color (Conant and Collins 1998). The head, neck and limbs are dark olive, brown or black with thin yellow, green or orangish stripes. There is also a oval spot located behind the eye of most specimens (Harding 1997). 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 longer thicker tail. The males vent also opens beyond the edge of the carapace whereas the female's open up the carapace (Harding 1997). The young map turtles have a pronounced dorsal keel and patterns on the plastron consist of dark lines bordering the scutes (Conant and Collins 1998). A hatchling has rounded gray 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 (Harding 1997).
The Common map turtle inhabits an area from southern Quebec and northwestern 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, northeastern Oklahoma, Arkansas, Tennessee, Alabama and then northwestern Georgia. It also occurs in the Susquehanna River system located in Pennsylvania and Maryland and also in the Delaware River (HSUS 1999).
Common map turtles inhabit ponds, river-bottoms and lakes. The abundance of aquatic vegetation is preferred (Kirkpatrick 1999). They prefer large bodies of water and areas with fallen trees and other debris for basking (Conant and Collins 1998).
Common map turtles breed in the spring and the fall. Most mating takes place in deep waters. The nesting period lasts from May to July. Unshaded sites with sandy soil is highly preferred (Harding 1997). The female usually chooses well-drained areas for depositing the eggs (Kirkpatrick 1999). 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 or September. When a nest hatches late, the common map turtle has been known to overwinter in the nest (Harding 1997). The female usually lays two or multiple clutches in one breeding season. The sexes of the young are determined by the temperature. 25°C incubation will give majority of males whereas 30-35°C will yield more females (Kirkpatrick 1999).
The common map turtle is dormant from November through early April. Most of that time is spent under the water, wedged beneath submerged logs, in the bottom mud of a lake or in a burrow. They have been known to change locations in the middle of the winter (Harding 1997). They are avid baskers and they bask in groups (Kirkpatrick 1999). They are diurnal, active both in the day and at night (Harding 1997). They are also a very wary animal, at the slightest hint of danger they slip into the water and hide (Kirkpatrick 1999). During courtship the male initiates by tapping his long claws on the front of the female but few details are known (Harding 1997).
Common map turtles are omnivores (Kirkpatrick 1999). The feeding always takes place in the water. The adult females, due to their large heads and strong jaws eat larger prey than the males. The females consume snails, clams, and crayfish. The males eat aquatic insects, snails, and smaller crustaceans. Both are also known to eat dead fish and some plant material (Harding 1997).
These turtles are sometimes, rarely, used as food. The pet trade hasn't taken an interest in the common map turtle, probably due to the difficulty of maintaining them in captivity. They also don't affect the fishing industry, other than getting caught on the hooks, since they do not eat any of the game fish (Harding 1997).
Common map turtles are less tolerant to poor conditions than most other turtles (Kirkpatrick 1999). Humans are hurting the turtles by numerous methods. Pollution, waterfront development is destroying their breeding sites, and automobiles are also a killer of these turtles when they are migrating to the breeding sites (HSUS 1999). Fishing also has a negative affect on them, they get caught on the fishing hooks (Harding 1997). Populations have been reduced or eliminated in some areas, but they do still persist in suburban rivers and agricultural lands (Harding 1997).
Melissa Donato (author), Michigan State University, James Harding (editor), Michigan State University.
Conant, R., J. Collins. 1998. Reptiles and Amphibians in the Eastern/Central North America. New York: Houghton Mifflin.
HSUS,Humane Society, .. 1996. "Amendments to Appendices I and II of the Convention." (On-line). Accessed November 13, 1999 at http://www.xmission.com/~gastown/herpmed/graptem.htm.
Harding, J. 1997. Amphibians and Reptiles of the Great Lakes Region. Michigan: The University of Michigan Press.
Kirkpatrick, D. 1993. ". An Overview of the Map Turtles of the United States." (On-line). Accessed November 13, 1999 at http://www.unc.edu/~dtkirkpa/stuff/maps.html.