Northern map turtles are small- to medium-sized and have a low ridge along the center of the upper shell. The hind edge of the upper shell is strongly serrated. The upper shell normally is brown or olive brown with a netlike pattern of fine yellow lines, giving the shell the appearance of a road map. The lower shell of this species is light yellow; the seams between scutes are dark brown. The head and limbs are brown with thin yellow lines. A small yellow spot is present behind each eye.
Similar species: To identify our 3 map turtles, look at the yellow spots near the eye. Ouachita map turtles have a large yellow marking behind each eye that extends, narrowing, on top of the head. False map turtles have a thick yellow line behind each eye that forms a backward L shape.
Upper shell length: 7 to 10¾ inches.
Occurs primarily in the Ozark region of Missouri and upper Mississippi River in northeastern Missouri.
Habitat and Conservation
Rivers, sloughs, and oxbow lakes are the preferred habitats for the map turtle. This species will spend much time basking in the sun on logs or other objects, but will quickly dash into the water at the slightest disturbance.
Map turtles eat mussels, snails, crayfish, and some insects, including the naiads of several species (such as mayflies and dragonflies). Female map turtles, which are larger than males, can crack the shells of mollusks, snails, and crayfish with their jaws.
Common. This species used to be called the “common map turtle,” but biologists recommend avoiding the word “common” in the name, since it might mislead people into thinking these animals are abundant, when in fact they simply have a broad geographical distribution. Broadly speaking, populations of amphibians and reptiles have been declining due to habitat destruction, indiscriminate use of pesticides, and pollution.
Usually active from late March until October, they may be somewhat active in winter. On mild, sunny days in December and February, you may see them swimming under ice or basking on logs. Courtship and mating usually occur from late March through May. From late May into July, females travel on land to find a suitable nest site, along a plowed field, or in a patch of sand or clay bank. There may be 1–3 clutches of 6–15 eggs per season. These usually hatch in late summer or early autumn.
The netlike pattern of fine yellow lines on the carapace of map turtles can look a lot like a road map, hence their name. This species is declining in much of its range and is listed as endangered in Kansas, Kentucky, and Maryland.
Although mussels, snails, and crayfish have evolved shells to protect themselves from predation, the predatory female map turtle has evolved strong jaws to crack those shells. Northern map turtles may turn out to be a blessing in places where the invasive zebra mussel is introduced.