The smaller the creature, the tinier the feet–and the less often we’re able to see the kind of detail that we’re accustomed to seeing in the tracks of larger creatures. So I was delighted a few weeks ago to find these beautifully revealing chipmunk tracks. T he one that first caught my eye was the right rear print that lies off by itself in the lower right part of the photo. The much larger rear print of a gray squirrel lies above it, and at least two other chipmunk tracks are visible among the unrelated disturbances in the upper part of the photo. The chipmunk’s right front print sits in the left part of the frame midway between top and bottom, and its left rear print can be seen above the squirrel track. The left front print isn’t obvious but a few small depressions suggest that it lies above the right front in the upper left quadrant of the photo. The chipmunk was moving toward the right.

The two right prints of the chipmunk show excellent detail, so I’ve focused in on them in the photo to the left. The toes and claw marks are visible, four of each in the front track (at the upper left) and five in the rear track (at the lower right). Behind the toes you can see the grouped depressions that make up the middle pads of both the front and rear tracks. For such a small creature those tracks are exquisite.

Why do I get so excited about such stuff? The finely formed details of animal tracks contain such energy and elegance that I just love to look at them. But beyond that, track details can reveal an animal’s affinities, in this case the affinities between chipmunks and other small rodents. The gray squirrel tracks in the next photo (moving toward the top of the frame, rear prints above and front prints below) help to illustrate the important features shared by this group. In the rear prints the central three toes lie close together and point forward, while the inner and outer ones sit farther back and are angled to the sides. The four toes of the front prints are spread more or less evenly. The middle pads of both front and rear feet are made up of four depressions, arranged in a crescent in the rear and a more triangular shape in the front. In the front print the heel pads, located just behind the middle pads, show as small paired depressions.

There are lots of rodents, and some have foot structures that depart from the characteristics I just described. But our most common small rodents–including one even smaller than a chipmunk–are surprisingly consistent in showing this suite of features. It took perfect mud to register the details in these white-footed mouse tracks (heading toward the top of the photo), but the family resemblance comes through clearly. The numbers and arrangements of the toes are the same, and the middle pads of both front and rear prints are similar to those of the chipmunk and the squirrel. You can even see the heel pads, albeit slightly smeared, in the front tracks!

Family resemblances can extend to the gait level as well, and they certainly do here. Widely placed rear prints and more narrowly placed front prints, positioned behind the rear ones, represent a typical pattern for bounding or jumping small rodents. Of course this pattern changes when different maneuvers are required, and even at a steady bound the four tracks aren’t usually as perfectly placed as the ones in the snow photo of the gray squirrel. But both gait patterns and track details are useful clues to the identities of our most common small rodents.