Map Turtles

By: Crystal Cockman

While walking out at High Rock Lake this past week, a friend stumbled across a really nice and intact turtle shell. Since it was in such good condition, I decided to pick it up and take it back with me. It looked different than some other shells I have found, so I emailed the picture to a herpetologist friend, who informed me it was a map turtle, likely a Mississippi map turtle (Graptemys kohnii). This is a species that is not native to North Carolina, but is a common pet, and has been introduced into High Rock Lake and potentially other Piedmont reservoirs.

Graptemys is a genus of aquatic turtles found in freshwater lakes in North America that are also known as map turtles. They get this name because they have a very cool contour-like design on their shell that resembles a map. They look much like other freshwater turtles including sliders and cooters, but have a distinctive keel that is found going down the center of their shell. They feed largely on mollusks and crayfish, and as a result there is some evidence that nonnative zebra mussels and Asian clams may benefit these species as a food source.

Mississippi map turtles take their name from the Mississippi river basin, and are found in Texas, Louisiana, Mississippi, along the Missouri, Ohio and Mississippi rivers north to Illinoi, Indiana and North Dakota. They are a popular pet, which is most likely how they have been introduced to our Piedmont North Carolina reservoirs.

The Mississippi map turtle is the only known species introduced in the state, though we do have a native map turtle in the far western part of our state, the common map turtle or northern map turtle (Graptemys geographica). Common map turtles are also found in freshwater lakes or rivers, preferring clear flowing waters, from Quebec south to Alabama. They spend the winter under water, sometimes hibernating in groups, and they are able to do this by absorbing oxygen from the water. Because they require more specific habitat than many other turtle species, they are less common in most places, and are listed as endangered in three states.

Biologists do not know much about the population or distribution of these nonnative map turtles, and are interested in any information folks can provide. If established, species like these could compete with native turtles for habitat and food. Therefore it is important if you do have one as a pet, to keep it secure and not to release it into a local water source. Turtles seem to be one of the more popular pets, and with a long live span can be one of the more frequently abandoned ones too, so it is important to consider carefully before purchasing one.

If you do have a turtle you cannot care for any longer, there are turtle rescue groups you can find online who will help advertise pets for adoption. Other environmental education facilities or even schools might also be interested, so explore every avenue in place of simply releasing any such pet into the wild. The impacts can be far-reaching on our native turtle and other critters if such species become established.