Category: mammal gaits

River Otters: Living in Two Worlds

I’m fascinated by river otters. Well, I guess I’m fascinated by all animals, but otters hold a special appeal. We humans can relate easily to their playfulness and sociability. The otter pictured below was photographed at the Lindsay-Parsons Biodiversity Preserve in Tompkins County, New York. This expanse of ponds, meadows, wetlands, and forests is one of many protected areas managed by the Finger Lakes Land Trust. It’s open to the public and is a great place to watch otters. And even if an otter doesn’t show itself while you’re there, you’ll probably find evidence of its presence in the form of tracks, scat, or resting areas.

Photo by Scott Levine, Finger Lakes Land Trust

Scat (sometimes called spraint) is probably the most obvious sign left by otters. Their diet of fish, crayfish, crabs, freshwater and saltwater mussels, and even small mammals and birds brings with it indigestible parts which end up in fecal material. In the center and upper left of the photo below you see formed scat containing crayfish shell fragments held together by finer material. The roughly tubular shape of these deposits indicates that they are relatively recent. Under the influence of rain and weathering otter scat readily disintegrates into scatterings of the more visible parts, like the fish scales at the lower right.

Scat is an important means of communication among otters and is usually placed in significant locations, such as on trails between bodies of water, near dens, and at resting areas. Popular locations may accumulate scat of varying ages, and the collections become especially large when several otters are using the area. In the photo below large piles of scat lie in the lower middle part of the frame, and smaller deposits can be seen both uphill and downhill. The entire area has a trampled look, and in the upper part of the photo, slightly to the left of center, there’s a slight hollow that is relatively bare of debris. It looks like both a comfortable resting spot and a good lookout over the river below.

Otters are fastidious about keeping their fur in good condition, and in addition to grooming, the animals do a lot of rolling. This dry wash technique removes both grime and water, helping to maintain the insulating qualities of the coat. Rolling spots may be in conifer duff, grass, soil, sand, or even in snow. The animal that made the roll in the photo below came out of the water from the ice hole at the left. Around the edges of the roll the snow was pushed outward by the otter’s feet, and in the center it was flattened as the otter writhed on its back. There are some nice tail marks at the upper right. After it rolled the otter went right back into the water, leaving a few tracks and a body slide on the left side of the photo. There’s a great video here that shows the playful energy of a rolling otter.

Sliding is another favorite otter pastime. While the animals will occasionally slide downhill on grass or mud, sliding reaches its apogee in snow. On good snow an otter can slide down hills, on level terrain, and even up slight inclines, using its feet only when needed to keep the joyride going. And joyride isn’t an exaggeration. Otters sometimes make repeated slides, turning around and going back time after time to enjoy another go.

And then there are tracks. Otter tracks are similar to those of other members of the Mustelid family, with five toes arranged asymmetrically on both front and back feet. The animal that made the tracks in the photo below was moving from lower left to upper right. The first print at the lower left is the left front, the next is the left rear, then comes the right front and finally the right rear. This pattern of front-hind-front-hind, and the space separating the first group of four from the next group, are typical of the lope, the otter’s preferred gait. Another cogent detail is the relative sizes of the prints. The rear tracks (the second and fourth in each group) are larger than the front tracks, a feature that distinguishes otter tracks from the similar-sized tracks of the fisher. The otter’s hind feet are webbed, and the toes can spread widely to make optimal use of the webbing when swimming. There’s a hint of webbing in the right rear print in the first group shown below, but webbing doesn’t always show in tracks. And as you can see from the photo, tail marks may not be present. In fact they’re rare unless the animal is moving in deep snow.

When otters are in the area they usually leave plenty of evidence, but you may miss it unless you look in the right places. These include silty or sandy shorelines, grassy or forested stream banks, ice-covered ponds and streams, beaver dams or artificial dikes, peninsulas, and trails or elevations between bodies of water. As you observe these places you’ll get a feel for convenient travel routes, good rolling spots, and preferred resting areas. Bluffs of banks with easy access from the water and padded with soft forest duff are always good places to check and often have tracks, scat, rolls, or other evidence of otter activity. The places otters choose are often the places I’d pick for a pleasant lunch stop. Looking down on a river from such a spot I can imagine an otter emerging from the water, loping up the bank, and making a quick check of the situation. Perhaps it examines scat left by another member of its family group and adds some of its own to the collection. Or maybe it enjoys a short rest and a good roll before returning to the water for more foraging.

The aquatic part of an otter’s life is mostly hidden from us, but as soon as it leaves the water an otter leaves evidence of its life on land. Reading those messages can give us glimpses into the lives of these truly remarkable animals.

Walking the Rails

When I was a kid I used to enjoy exploring the woods and fields near my home, and one of my routes involved travelling along a seldom used railroad line. The rocky bed that supported the ties and rails was hard to walk on, and the spacing of the ties was just a little different from my natural step, so I often walked on one of the steel rails. Recently I found myself doing the same thing–walking along a seldom used railroad line and attempting to keep my balance as I walked on a rail. As I stepped carefully along I saw some peculiar muddy smudges on the rail ahead of me.

I thought at first that someone with muddy sneakers had been there ahead of me. But the marks didn’t look like the tread pattern of a shoe, and some of the groups of muddy spots seemed to form zig-zags rather than the centered prints that a person would make. My puzzlement turned to delighted comprehension as I noticed more details. The zig-zag sections were separated by areas that were smeared or had a jumble of muddy marks, such as the the area at the top right in the photo above. It was as if a walking animal had occasionally lost its balance and shifted its steps to keep from falling off the rail.

In the clearest impressions, arrays of small mud spots seemed to form half-circles around central clusters of smudges, as in the two photos below. The more I looked at them, the more the outer marks looked like toes and the inner clusters like middle pads. And those half-circles of widely separated toes, spreading across most of the top of the rail, could only have been made by an opossum.

Compare the images above with the photo of opossum tracks in mud (from a different opossum encounter) below–the left front track at the upper right and the left rear track below. Notice how the widely spread front toes encircle the middle pads; the upper two middle pads show as triangular impressions and the lower two as faint roughenings of the shiny mud surface. Four toes of the hind print point toward the upper left and the innermost hind toe–probably superimposed on the innermost front toe–points toward the right. The front print is a pretty good match for the mud-on-steel prints in the photos above.

Here’s another shot (from last winter) of opossum tracks, the left front on the right and the left hind on the left. The perfect tracking snow recorded the triangular to oblong middle pads of both front and rear feet beautifully. In the front print the position of the middle pads inside the circle of toes reproduces the positioning of the inner clusters and outer circles of mud marks in the tracks on the rail.

The positioning of the rear feet of a walking opossum is often erratic, and the animal that walked on the rail left many rear tracks that were smeared, distorted, or partly missing. In the photo below the middle pad area of the left rear foot (on the left side) made the large smudge behind the left front print (on the right), and the four outer toes of the rear track left spots and smears on the sloped upper edge of the rail. The lack of precision in the placement of its rear feet may have caused some missteps as the opossum attempted to balance on that three-inch rail.

Putting it all together, the whole scene made sense. I found the muddy slough the possum had crossed, coating its feet in ooze, before it climbed up onto the railroad bed. There were sloppy smears and spatters on the rocky shoulder of the railroad bed, and on the ties where it had first stepped onto the rail. The zig-zag pattern of the walking gait was occasionally punctuated by sections with extra steps and smeared mud where the opossum had struggled with its balance. (What would it look like if a more precise walker–like a cat–had left muddy prints on a rail?) At each step mud was transferred from the opossum’s feet to the rail, and the tracks grew fainter and finally disappeared. I continued in the same direction toward a road bridge which crossed the railroad line. Under the bridge there was a wide, dusty area, and when I stepped away from the tracks to investigate I saw a recently made opossum trail. Could it have been the same animal? I can’t be sure, but I feel a kinship with the opossum that made the muddy tracks. In spite of our balance problems we both found walking the rail to be a good way to get where we wanted to go.

Raccoon Spring Fever

Winter is still with us, but the season is advancing and mild days are beginning to outnumber the cold ones. Raccoons have spent the frigid periods in a state of torpor, denned up in hollow trees, rock crevices, second-hand burrows, or perhaps under your porch. On warm days the animals emerge from their winter dens and roam about in search of food and mates. Their habitual use of a gait called the pace-walk gives their trails a unique and easily recognizable appearance.

In the pace-walk the tracks lie in sets of two, each set made up of front and rear prints from opposite sides. One of these prints generally falls ahead of the other (although they can be perfectly even). In each successive pair the sides of the front and rear tracks switch and, if they are uneven, the leading side also switches. In the photo above the larger hind prints lie ahead of the smaller front ones. The succession of tracks, starting at the lower right corner, is: left front with right rear, right front with left rear, left front with right rear, and right front with left rear.

Raccoons are not good at digging, and as long there’s a substantial snowpack they have difficulty getting at edibles in the leaf litter. But seeps and unfrozen streams are not only free of snow and ice–they also harbor tasty morsels like aquatic insect larvae, worms, snails, and other invertebrates. Seeps are likely to form during mild weather, and they’re usually found in the same places each year. Muddy tracks like the ones below tell us when raccoons have been visiting them.

There are two separate passages in the photo above, the upper one heading from left to right and the lower one going in the opposite direction. If you focus on the darker tracks in the middle of the photo, you can see the similarity between the patterns in the two photos. But in addition to being more irregular, the mud-on-snow tracks have a slightly different arrangement. In each set of two the larger hind foot touched down a little behind the smaller front foot. This, and the fact that the steps are shorter, tells us that the animal was going slower. The icy crust was probably slippery and the raccoon needed to be more careful with its footing.

As spring–and mud season–draws closer, raccoon tracks can be found in all sorts of wet places. When the photo below was taken a thin blanket of snow covered most of the landscape, but the silty stream margins were clear and unfrozen. The small tracks heading in both directions were made by minks, and the larger ones belong to a raccoon. There’s a pretty clear hind print near the right edge of the frame, but the other raccoon prints (one to its left and another toward the bottom of the frame) are distorted because the animal slipped in the mud. In fact the very weird track at the lower edge of the photo is actually two prints, one on top of the other. Apparently the heavier raccoon had more difficulty with its footing than the smaller minks did.

Here’s another trail made by a pace-walking raccoon on a nicely moistened sand road. The pairs of prints are a little closer together than the ones in the first photo, and the rear tracks fall slightly behind the front–both signs of lower speed. Maybe with its feet sinking slightly in the soft sand the animal chose to move more carefully, or maybe it just wasn’t in a hurry. On a mild spring day even a raccoon might feel like taking it easy.

A Closer Look at Deer Tracks

A deer track–so familiar that we may pass it by without paying much attention. But a closer look at a deer track can reveal some unexpected insights. In the photo above the two main toes (called clouts or claws) show as paired depressions separated by a ridge. In each clout the broader rear edges are rounded and the narrower forward ends are bluntly pointed, so the direction of travel is to the right. When the toes are placed close together the way they are in this photo, the overall shape is vaguely heart-shaped.

Here’s another shot of deer tracks, in this case a left front (at the lower left) and a left hind (at the upper right). Front prints tend to be slightly wider and more rounded than rear prints, but the differences between front and rear are not nearly as pronounced as they are in most other mammals.

Now look at the first photo again: it’s actually a rear print superimposed almost exactly on top of a front (which trackers call a direct register). The clue to the double impact lies in the right toe impression: along the leading part of the outer margin there’s a slight crack and a sloping edge. The outer edge of the left clout is more like a vertical cliff. The left outer edge of the rear foot came down even with the left edge of the front, but the right outer edge landed a little inside.

It helps to have a track pattern when wrestling with such matters. The deer in the photo below was doing an ordinary walk (also called the diagonal walk, for reasons connected with the footfall sequence), and it left the zig-zag track pattern typical of the gait. Each “print” is actually made by two feet, first the front and then the rear on the same side.

The next photo shows the double impact more clearly. In each impression you can see part of a front track with a rear on top and slightly behind (know in tracking circles as an indirect register). I call this the ordinary walk because it’s one of the most common gaits of both wild and domestic animals (and because the term is less abstruse than ‘diagonal walk’), but it’s only one of many variations on the walk. The patterns associated with the various kinds of walks vary, but if you can recognize the zig-zag arrangement of the ordinary walk you’re well on your way to understanding these and other gaits.

But how does that pattern come about? Gaits can be hard to understand, especially if you haven’t spent much time watching animals move. Fortunately there are lots of helpful videos available to make up for this lack. Here’s one that shows the ordinary walk really well: https://www.bing.com/videos/search?q=animal+tracking+gaits&view=detail&mid=11CC299AF70EC963C01211CC299AF70EC963C012&FORM=VIRE.

You should go past the galloping dog and the trotting horse and focus on the third sequence, a horse walking in slow motion. You’ll see each hind foot landing in the place just vacated by the front foot on the same side. If you’re curious about the variations I mentioned there are a few later in the video. For example the first cat sequence is an overstep walk, in which the hind foot passes the front foot track and lands just ahead of it.

When a deer is moving faster or more erratically its tracks can look very different. In the next photo of a left rear print, the ridge separating the clouts widens out toward the front. Note also that the two toe impressions don’t look the same: the left one is relatively level but in the right one the tip area and right edge are deeper. This suggests an energetic turn to the right, and this deer was, in fact, making a playful jump to the right.

The deer tracks in the photo below are even less like our idealized image of deer tracks. This animal was galloping from left to right in soft, moist sand, and its feet sank in so much that both the main toes and the dewclaws made deep impressions. These are both left feet, the front on the left and the rear on the right and the differences in the front and rear dewclaws show nicely. In the front track the dewclaws are closer to the main toes and are angled sideways, while the hind dewclaws are slightly farther behind and point more forward. The energetic movement caused the tips of the toes to sink more deeply than the back parts of the clouts. When the feet came up out of the sand the toe tips dragged and parts of the track walls were broken and scattered, adding to the atypical appearance of the tracks.

If we recognize the kinds of differences I’ve illustrated we can go far beyond basic track identification. Track variations can tell us about the movement and energy of the animal, what it was paying attention to, and maybe even why it was moving the way it was.

Spring Fever among Woodchucks

If you think you have it bad, just consider the woodchuck. The males emerged from hibernation weeks ago only to find the ground covered with snow. There wasn’t much to eat, and the weather wasn’t very spring-like. But no matter–they were more interested in procreation than food or comfort, and they spent their time searching out burrows occupied by females. Upon finding a receptive female the male entered the den and copulated with her, then moved on in search of another one. With nothing much to eat the roaming males, which may have dropped up to 1/3 of their body weight during hibernation, lost even more body mass. Meanwhile, the female woodchucks remained underground and got a few more weeks of sleep.

This delayed emergence is important because, like the males, female woodchucks have already lost weight during hibernation and losing even more would impair their ability to give birth to healthy young. Their appearance above ground coincides with the onset of new spring growth and their condition improves rapidly.

I found the den pictured below in early March. A few inches of new snow covered about a foot of denser old snow, which made for nice tracking. There weren’t any tracks beyond those shown in the photo, so it looked like the animal came out, took a look around, and then went back into the burrow. The mud-on-snow tracks are remarkably clear–check out the right front print just to the right of center.

Finding such unmarred tracks around burrows becomes less likely as the season advances and the animals make more forays to and from their winter refuges. The photo below, also from early March but taken a few years ago, shows the muddy and partially melted evidence of several trips. In both of these cases the weather was still pretty cold and there was a substantial snowpack, so these were most likely males in the throes of spring (or rather mating) fever.

As winter loosens its grip woodchuck tracks start becoming more widespread in fields and forest edges. In the photo below the direction of travel is from the lower left of the frame to the upper right, and the impressions form a zig-zag pattern. Each angle of the zig-zag is composed of two


tracks, the rear positioned roughly on top of or close to the front track from the same side. These are the characteristics of the indirect register walk, the woodchuck’s most common gait. Starting from the lower left, the sequence in the photo above is right hind on right front, left hind on left front, right front with right hind just ahead, left hind on left front. To the right of the first set of left front and hind there are some gray squirrel tracks heading in the opposite direction.

By the way, woodchucks are also known as groundhogs, but I prefer the name woodchuck, because the word derives from one of its Native American names. Woodchucks weren’t as common in pre-colonial times as they are now, but their populations would have been concentrated around cultivated fields so they would have been familiar to Native Americans. They still thrive in agricultural landscapes, and are sometimes seen as pests. From an ecological point of view they are actually beneficial. Woodchuck excavations help to turn over and aerate soils, and their burrows provide homes for many other animals.

The photo above shows a burrow I found after a very cold night. Rabbit tracks led both in and out, but this hole wasn’t dug by a rabbit. Unlike European rabbits, which construct extensive tunnel systems called warrens, our cottontails don’t dig burrows. They get along just fine without underground housing, unless it’s very cold. When that happens they find shelter, and that shelter is often a woodchuck burrow.

An Encounter with a Fisher

Sightings of wild mammals are generally rare, and when they do occur it’s usually just a quick glimpse of the tail end of the animal as it flees at top speed. So my recent encounter with a fisher was doubly unusual. I was walking downhill on a sloping section of forest road (Hammond Hill Road in Hammond Hill State Forest for those who know the area). That part of the road is straight so I could see pretty far down the hill, and I suddenly realized there was a dark animal moving around on the road far below. I froze, not sure at first what kind of animal it was and hoping it wouldn’t realize I was there. It didn’t–in fact it actually began coming up the hill toward me. As I got a better view of its elongated body, short legs, and long fluffy tail I realized it was a fisher. I watched as it moved in a completely relaxed manner–apparently unaware of my presence–and marveled at its beauty. I was afraid if I made a move to get out my camera the fisher would take off, so I didn’t dare try for a photo. But here’s a good photograph of a fisher obtained from the Vermont Center for Ecostudies (https://vtecostudies.org/blog/walk-with-the-fisher-on-outdoor-radio/).

Photo courtesy of the Vermont Center forEcostudies

The fisher continued to move uphill in my direction at a steady bounding gait, with an occasional pause to look around. When less than 50 feet separated us, it suddenly realized I was there. It stood up on its hind legs, stared at me for a few seconds, and then bounded off into the trees.

Of course I immediately went to look at the tracks. Because the snow was dry and fluffy most of the prints weren’t clearly defined, and the cloudy conditions made things even harder to see–and nearly impossible to photograph. But there was a spot farther down the hill where the snow was firmer and the track details showed up better. A set of four prints from that part of the trail is shown in the photo below (direction of travel from right to left). The pattern

Track sequence, starting from the right: right front, left front, right rear, left rear.

resembles the bound of a cottontail rabbit: the two front tracks are narrowly set behind the rear tracks, and one (the left front) leads the other. The rear tracks are more widely separated and almost even with each other. Typical mustelid structure shows in the prints: the five toes are arranged in a lopsided crescent and the middle pads form a smaller crescent behind the toes.

That was only one of several different gait patterns I saw as I backtracked along the fisher’s trail. In true mustelid fashion the animal had been very flexible in the way it placed its feet. Rather than showing the rather poor photos from that day I’ll illustrate two of the variations I saw with shots that I took on other days (the direction of travel again is from right to left). As in the opening shot the four tracks in the photo below are well separated, but the rear prints are staggered rather than even with each other, and one is positioned slightly behind the leading front print.

Track sequence, starting from the right: right front, right rear, left front, left rear.

In the next shot the left rear foot came down on top of the left front, leaving a pattern that looks at first like there are only three tracks. But in the heel area of the middle impression there’s an inner ridge and a wider area of disturbance to its left, showing that two feet did actually land there.

Track sequence, starting from the right: right front, left rear on top of left front, right rear.


In addition to those two there were other variations–changes in the leading front or rear foot and slightly different placements of the second and third feet to hit the ground–but to my eyes the fisher’s bounding movement appeared to be uniform and unvarying. Except for momentary pauses it moved steadily uphill with the gently arching leaps that are so typically mustelid. One difference did stand out, and that was a variation in the leap lengths: the four-print patterns that matched the one shown in the first photo were separated by slightly longer distances than the patterns shown in the second and third photos. The fisher apparently wanted to move faster, and I suspect that the more even placement of the rear feet in the first photo delivered more power and enabled longer leaps. But there were many variations in the patterns that didn’t involve any changes in leap length, so there must be other factors that cause a fisher to vary the way it places its feet. I can only imagine the subtle interactions that go on between the animal and its surroundings. I hope that with further study of fisher trails, and maybe even some additional encounters with fishers, I’ll be able to understand more of the puzzle.

The Ups and Downs of Snowshoe Hares

Snowshoe hares are having a banner year. In early December I spent some time in the western Adirondacks, and it seemed like there were snowshoe hare trails everywhere. A bounding hare-like its cousin the cottontail rabbit-typically leaves sets of four prints in Y shaped arrangements. The two larger rear prints are usually even with each other and widely spaced while the smaller front prints are behind the rear, staggered,  and placed along the center line of the trail. 

In the photo at the right (direction of travel from right to left) the hind tracks are the larger and somewhat triangular prints on the left side. The right front print is near the center of the photo and the left front print is behind it toward the right edge of the frame.

The hare that made the tracks above didn’t sink very far into the snow, so it’s easy to see all four prints. But when temperatures stay low and the snow keeps falling there may be a foot or more of light, fluffy stuff on top that doesn’t offer much support. That’s the way it was during my recent Adirondack visit. Even the snowshoe hares were sinking deeply at every leap, and their landing patterns didn’t look the same.

In the photo at the left a bounding hare traveled from bottom to top, leaving a triangular hole each time it landed. At each landing the front feet plunged into the snow at the narrow lower part of the triangle. The more widely held hind feet–each foot spread out laterally for maximum support–landed just past the front feet to form the wide upper part of the triangle. The width at the widest part of these craters can approach twelve inches.

Snowshoe hares, like cottontails, tend to use the same travel routes repeatedly. This creates trails that offer firmer footing and easier movement, like the one shown at the left. I’ve read that these trails help the hares escape from predators, but I’m not sure about that. Maybe the predators can move more easily as well.

Snowshoe hare populations are known to go through cycles of abundance and scarcity. These cycles are especially pronounced in the Boreal forests of Canada, where population numbers of the Canada lynx are closely tied to the abundance of hares. The Adirondacks host a greater variety of both predators and prey–although there are no lynx–and population fluctuations don’t reach the same extremes for either prey or predators. But when hares are more abundant than usual, as they seem to be in the western Adirondacks this winter, young fishers, coyotes, and bobcats–the main predators of snowshoe hares in this region–are more likely to make it through their first winter. I hope to visit the same locations over the next few months, and I’ll be paying special attention to the tracks and signs of all the animals in the web of relationships that includes the snowshoe hare.

Lessons from Flying Squirrels

The weather has been unusually cold and snowy for early November, and there have been days when conditions were perfect for seeing detail in the tracks of small animals–an icy base with about half an inch of new, soft snow on top. On one of those days I went to a location where I had seen flying squirrel trails in past years, and I found some beautifully detailed prints. In the photo on the right (direction of travel to the right), the right rear track is at the bottom of the frame, and the right front is just above it. The other two prints are at the top, the left rear just behind the left front. The toes  and middle pads show up nicely in both front and rear tracks. The heels of the rear prints made impressions, and the paired heel pads of the right front track  can also be seen.

Now compare the shot above with these chipmunk tracks, photographed on the same day and arranged almost identically except that the left front track is just below the left rear. There’s a similar amount of detail, with toes and middle pads clearly visible in both front and rear feet and the paired heel pads showing in both front feet. I had hoped that if I found really detailed tracks I would see features that would separate chipmunks and southern flying squirrels, but to my eyes there are no appreciable differences between the tracks in the two photos. The dimensions are similar as well: both sets of prints have a trail width (the distance from the right edge of the right rear print to the left edge of the left rear print) of 2 inches, and the length of the front track is 9/16 inch for the flying squirrel and 5/8 inch for the chipmunk, not significantly different. So how did I know that the tracks in the first photo were made by a southern flying squirrel, while those in the second belonged to a chipmunk?

The answer came from the differing trail patterns. Southern flying squirrels have flaps of skin (patagia) that connect the front and rear legs all the way out to the ankles, so they move differently from chipmunks (and also from tree squirrels, for that matter). The front tracks of a bounding southern flying squirrel are set almost as wide as the rear, and they are usually in front of, or occasionally between, the rear tracks. Because of the skin flaps, flying squirrels are not as fleet-footed on the ground as other small rodents, so their leaps are shorter. Compare the southern flying squirrel bounding trail in the photo above (traveling from bottom to top) with the next photo of a trail made by a chipmunk (traveling from top to bottom). In its normal traveling bound the chipmunk consistently places its rear feet ahead of its front, and its leaps can be much longer than those of the flying squirrel. Of course chipmunks do sometimes make short leaps, and they do sometimes place their front feet between (as in the second photo of the blog) or ahead of the rear. That kind of pattern in a chipmunk trail is an indication of a break in the rhythm, while it falls withing the normal bounding pattern for a southern flying squirrel. (By the way, neither of the bounding photos came from the day I took the close-up shots, but they illustrate the trail patterns I saw that day.)

More snow changes everything. All bounding animals switch to what I call a double-register bound when their feet sink deeply into the snow. The trail pattern consists of sets of two impressions more or less side-by-side, created when the rear feet come down in the holes just made by the front feet. For an animal the size of a flying squirrel even a few inches of soft snow can be enough to change its gait pattern from its normal bound to a double-register bound like the one in the photo at the right (direction of travel from lower right to upper left). The relative positions of front and hind prints no longer apply, but trail width can still be measured, and this trail had a trail width of 2 1/8 inches, squarely in the range for the southern flying squirrel. A chipmunk trail would have had a similar trail width, but the trail pictured above was made during a long stretch of cold weather. Chipmunks wait out winter’s coldest periods in a state of torpor in their underground refuges, while flying squirrels come out regularly even in frigid temperatures.

Feet Tell the Story: Family Resemblances Among Small Rodents

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. The 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.

The Graceful and Adaptable Mink

The mink is one of my favorite animals, so I’m always happy to find tracks like these, from a Tracking Club outing a few weeks ago. The marks made by the toes (5 on both front and rear feet) are small and oval or tear-drop shaped, and they form lopsided crescents around the middle pads. The claws may show as tiny pricks or as pointed extensions of the toes. The smallest toe lies on the inside of the track and farther back than the other toes, and it doesn’t always show. The mink that left these impressions was fidgeting around on a patch of stream side mud (the water is visible at the upper left) and the clear prints are mostly from the front feet.

But the beauty of mink tracks goes beyond the delicacy of individual prints–the trails that these animals make are equally fascinating. Here are the two front and two rear tracks of a mink arranged in a pattern often seen in mink trails. The first track at the lower right is the right front, and the last one at the upper left is the left rear. In the center of the photo the left front is on the left and the right rear is on the right. The animal was loping from the lower right to the upper left, and the order of footfalls was right front, left front, right rear, left rear. A mink traveling on stream ice a few winters ago left a string of similar four-print patterns. In the center of each grouping the left front print is slightly behind instead of ahead of the right rear, but otherwise they’re a good match with the previous photo, with the same direction of travel and order of footfalls. Notice how the four-print groupings are separated by spaces with no tracks–a characteristic of lopes and gallops. When I see trails like this I can picture the mink doing its easy, ground-covering lope, its spine curving and extending with each landing and take-off. I couldn’t find a video of a loping mink that I liked, but I did find one of a fisher (closely related to the mink) doing the same gait. Watch it here.

Stream edges are great places for finding mink tracks, especially if there are  roots or debris piles where prey animals can hide. The patch of sand visible in the center of this photo captured the tracks of a mink that was hunting in the surrounding tangle of logs and branches, deposited by a big flood several years ago.

But minks are resourceful when it comes to finding food. Last spring I was walking by an old log landing and I noticed a drying mud puddle. I’m always interested in mud so I went over to take a look, and to my surprise found mink tracks around the edges. There was a small pond nearby, but otherwise not much water, and I didn’t understand why this place–just a big area of bared mineral soil with a few mud puddles–would interest a mink. But the tracks were plentiful and very clearly mink. In the photo on the right the mink tracks run from lower left to upper right, and the big prints in the middle belong to my dog. As I moved around the edge and pondered, the mystery resolved itself. A leopard frog leaped from a grass clump into the water, then another one jumped, and then several more. Some enterprising mink had discovered the puddle, perhaps just as the tadpoles were transforming into frogs, and made use of the easy dinner. There were still plenty of frogs left to spend their summer feeding in the surrounding forest, overwinter deep in the soil, and then mate and lay eggs in the puddle next spring.