Turtles on the Move

One spring a few years ago, as I wandered along the banks of my local stream, I came upon a wood turtle engaged in digging a hole in a gravel bar. She was preparing to lay eggs, and she seemed to be laboring mightily. The spot was very rocky and she wasn’t making much progress.

Finding a turtle in the process of egg laying isn’t that common, and wood turtles themselves are scarce, so this was a very exciting find. But not wanting to create any more difficulty for her, I took a few photos and left. I don’t know whether she succeeded or whether she gave up and looked for an easier location.

Turtles usually find places that are more favorable for digging, like the sandy spot in the photo below. But the eggs in that nest didn’t mature. When young turtles hatch successfully they break out of their shells underground and make their way to the surface without creating much disturbance. The presence of signs of digging and shell fragments on the surface means that the nest was raided and the eggs were eaten, perhaps by a raccoon or a fox.

Although late spring and early summer are the peak times for reproduction, turtles may continue to mate through the summer and even into the fall. Pairing up and egg laying generally involve a lot of travelling, and these wide-bodied and low slung animals leave distinctive trails. The trail below was made by a diamond-back terrapin moving from bottom to top. Each line of impressions was made by the front and hind feet on one side, and the small front tracks alternate with the larger rear tracks. Between the two strings of prints you can see disturbances made by the dragging plastron, and at the very bottom of the frame there’s a small tail mark.

This turtle was walking, but the pattern looks very different from the patterns we see in walking mammals. That’s because the terrapin’s wide body and short legs prevent it from walking the way most mammals do. The turtle was doing an understep walk, the rear foot consistently coming down behind the spot where the front that moved forward just ahead of it was placed. The rear feet touched down about midway between the last front track and the one before that, so the spacing between prints is roughly even.

Here’s another turtle trail, this one made by a painted turtle moving from top to bottom on hard sand. The tracks consist mainly of claw marks, and they lie in sets of two, each set made up of a front followed by a rear. Both front and rear feet have five claws, but the front prints turn inward while rear prints point straight ahead. The gait in this photo is also an understep walk, but the hind tracks are closer to the front tracks than in the preceding example. Although the relative positions of front and rear prints can vary, turtle trails are always variations on the understep walk.

The trail in the photo below was made in dry sand, and the dragging plastron made a wide, smooth mark between the two track lines. Clear prints are not present, and it’s not obvious which way the turtle was going. Two kinds of evidence suggest that the direction of travel was right to left. First, the plastron drags seem to have smooth slopes on their right sides and steep edges on their left sides. And second, the deep holes made by the feet have drag marks pointing to the left.

Turtles are on the move, and their journeys can take them through a variety of habitats. Any area of sand, silt, or mud might show their unique parallel strings of prints and, sometimes, whimsical designs. So when you get a chance, take a detour and check out that patch of sand or muddy shoreline.