The eight species of aquatic turtles that may be found in our region present a more complicated variety of overwintering strategies than do box turtles.

Most of them are active from mid-March (some earlier) through mid-November (some later). And most overwinter by digging into mud below water in a lake, pond, or stream, with the common snapping turtle going as much as 18 inches deep. The yellow mud turtle and slider turtle (“red ears”) may burrow into a muddy bank above water. The false map and Ouachita map turtles may choose a muskrat den.

Data collected by a former biology colleague who now studies turtles in a lake in northern Wisconsin suggest that some of them move around during the winter. Maybe some of our turtles also exhibit winter wanderlust.

But I gotta tell you about the little spotted turtle whose overwintering heart and respiration rates I studied for a couple of years in Ohio. They live in a fen, which can most simply be described as a cold-water marsh. The fen water, cold even in summer, comes out of the southern end of a long glacial terminal moraine. The turtles aggregate and overwinter in chambers (hibernacula) they hollow out in the fen. The water-filled chambers freeze over in the Ohio winter, and to get turtles I would break the ice, reach in and gather them, and place them in a bucket of water and ice cubes for transport to my lab—and later, back to their hibernaculum. The hibernaculum water temperature always was 33-34 degrees Fahrenheit in the dead of winter.

The turtles even would swim around a bit in the simulated hibernaculum I had built in my lab where the water was kept at the same temperature. Using a polygraph and electrodes, and confining the animal being tested to a small recording chamber, I monitored heart rates in such water. A routine heart rate was in the range of 4-12 beats per minute. But one critter gave me one heart contraction every two minutes! Our turtles are decidedly tough little dudes!