Rodents are the most common mammals on earth, in both number of individuals and number of species. They are also the most diverse, with lifestyles that range from semiaquatic through fossorial (adapted for digging and living mostly underground), terrestrial, arboreal, and even semi-aerial (gliding flight). But don’t let that mind-boggling profusion intimidate you. In our region many of the most common rodents are members of the squirrel family, a group that is remarkably uniform in physical features. Fortunately for the tracker this uniformity extends to track details and track patterns, and familiarity with the key features will aid in the recognition of any member of the group.
In the photo below you see tracks made by a gray squirrel bounding toward the top of the photo. The five-toed rear tracks lie in the upper part of the image, and the four-toed front tracks can be seen in the lower part. Claw marks show as tiny pricks ahead of the toes of both front and rear tracks. Notice that the toe pads of the three middle toes of each hind print are lined up close together, while the inner and outer toes lie farther back and angle to the sides. Behind the toes you can see a C-shaped grouping of middle pads. The front tracks have only four toes, but again the central two point more forward while the outer and inner ones point to the sides. C-shaped arrays of middle pads sit behind the toes of the front prints, and heel pads (there are two on each foot, but it’s hard to tell in this image) are situated behind the middle pads.
Bounding is the most common gait for most members of the squirrel family, and the resulting pattern is another recognizable trait of the group. In the photo above the two rear prints are almost even with each other and are set wider and well ahead of the front ones, which are also nearly even with each other. This positioning may seem odd, but there’s a logical explanation. At each bound the animal lands on its front feet and draws its rear feet forward so they pass outside of its front legs. As the front feet lift off the rear feet touch down–ahead of the spots the front feet just left–and propel the next leap.
The next photo shows a bounding pattern made by a red squirrel, again travelling from bottom to top. There’s a striking similarity to the first image of the gray squirrel tracks, in both overall arrangement and track details. Because the substrate was softer the rear feet of the red squirrel (in the upper part of the frame) sank in deeper–notice that the whole length of each of the three middle toes registered as a narrow groove. Nevertheless the three toes are closer together and oriented more forward than the outer toes, just as they were in the gray squirrel tracks. In the front tracks of the red squirrel (in the lower part of the photo below) the claws show as grooves rather than pricks, but the overall structure is similar to the front tracks in the preceding shot. If you look at the red squirrel’s right front print (at the lower right in the photo below) you can see clear impressions of the two heel pads.
The chipmunk tracks in the next photo (again bounding toward the top) are consistent with the features we saw in the red and gray squirrel prints. In the right rear print (in the upper right quadrant) you can see that the middle toes are closely grouped and the inner and outer toes are angled to the sides. The left front track (in the lower section a little below and to the left of the right front track) shows the four clawed toes, the C-shaped grouping of middle pads, and the two heel pads.
Mud is great, but winter is also fine for seeing squirrel family connections. In the photo below of red squirrel tracks in snow (bounding toward the top, of course) you see the same characteristic features you saw in the mud tracks. As sometimes happens, the heel area of the right rear foot (at the upper right of the photo) registered as a flattened area behind the middle pads. (If you look back at the first photo of the gray squirrel prints you’ll notice that the heel area of the left rear foot also made a slight impression.) There’s a variation in the arrangement of the front tracks, with the right front well behind but the left front farther forward. This kind of foot placement is often seen in squirrels, but is less common than the more four-square pattern.
Flying squirrels possess gliding membranes (the patagium) which extend between the front and rear legs, and because of this the rear feet can’t pass as far ahead of the front feet as they do in red or gray squirrels. In the next photo you see a bounding pattern made by a southern flying squirrel (oriented toward the top) in which the front prints are situated between rather than behind the rear prints. In northern flying squirrel trails the front prints often lie ahead of the rear ones. Another special flying squirrel trait is the thick covering of fur on the undersides of the feet. Because of this flying squirrel prints rarely show the crisp detail found in the tracks of other members of the squirrel family. But even with these differences, flying squirrel tracks will remind you of the tracks of other squirrels.
In the next image you see a bounding pattern made by a woodchuck. If you didn’t realize that woodchucks belong to the squirrel family, the familiar features of their tracks should make that clear. Woodchucks are more likely to walk than bound, and when a woodchuck does bound it usually places its front feet in a staggered pattern rather than even with each other, as in the photo. Nevertheless, the overall arrangement and the track details are consistent with those of its relatives.
To complete the picture for small rodents in the Northeast we need to add a few creatures that don’t strictly belong in the squirrel family but leave distinctly squirrel-like prints. These include white-footed mice, meadow voles, and their allies. I include mouse and vole allies because each one represents a group of closely related species which are difficult to distinguish from tracks alone.
First, let’s look at tracks of the white-footed mouse, shown below in a bounding pattern heading toward the upper right. In spite of its smaller size, the animal made tracks that are uncannily similar to the tracks in the first three photos. If I didn’t tell you that an individual rear print is just half an inch across you’d be hard pressed to tell these tracks from squirrel tracks.
Vole tracks also show striking similarities to the tracks we’ve already discussed–but with a few important differences. In the next photo you see tracks made by a meadow vole bounding from bottom to top. The track sequence, starting at the bottom, is: right rear, right front, left rear, left front. This staggered arrangement is common in vole trails and differs from the more consistent four-square bounding patterns usually seen in white-footed mice and tree squirrels. Voles can leave more regular bounding patterns, but they often move at something between a bound and a lope and their track patterns tend to be more variable. The toe impressions in vole tracks also tend to be more finger-like than the toes of mice. In spite of these differences the tracks of voles will remind you of mouse and squirrel tracks.
This is all well and good, you may say, but if these creatures are so similar to each other, how can I tell them apart? I’ve mentioned a few variations that can be helpful, but often the most useful trait is size. There’s a neat size progression, and although there’s some overlap between adjacent species it’s usually possible to make an identification with a few measurements combined with other clues. There are two dimensions to consider: track width (more reliable than track length) and bounding trail width (measured perpendicular to the direction of travel across the widest part of a bounding pattern). I’ll focus on the big picture rather than giving an exhaustive account of the numbers–detailed measurements can be found in any good tracking guide. White-footed mice and the smaller voles (woodland voles, for example) are the tiniest of the lot, and meadow voles are slightly larger. Chipmunks come next, and southern flying squirrels are slightly larger than chipmunks. Northern flying squirrels outweigh their southern kin, and red squirrels are larger yet. Gray squirrels beat out red squirrels, and woodchucks complete the series. These differences in body size are reflected in differences in track and trail dimensions, so a few measurements are usually sufficient to clinch an ID. Even when the tracks you’re dealing with are in the overlap zone there are usually other clues that can point toward an identification. And when all else fails, it’s okay to say you just can’t be certain. If you treat each situation as a learning experience, you’ll find yourself stumped less and less often.