mammal gaits – Page 2 – Linda J. Spielman

When Trails Cross

Was the fox afraid of the fisher? Did the coyote chase the rabbit? Questions like these often come up when we find animal trails that intersect. And as always, the tracks tell the story. In the photo below a coyote trotted along a forest road, the direction of travel from upper left to lower right. A rabbit bounded across the road, leaving a trail heading from right to left. Both trails had been made early on a cold morning, and I came upon them not long afterwards. Neither trail showed any changes in pattern or speed in the vicinity of the intersection (although the rabbit took a few slow hops as it entered the road). The tracks in the photo tell us that whichever animal came second, it wasn’t alarmed or excited by the trail it was crossing.

Here’s another example: A coyote had trotted from upper right to lower left, and at least a day later a fisher loped from lower right to upper left across the coyote’s trail. The unchanging pattern of the fisher trail tells us that it had no apparent reaction to the older coyote trail.

In the next photo you see another instance of a fisher crossing a coyote trail. The coyote was trotting towards the upper right, and the fisher loped from right to left. But this time the tracks near the intersection reveal a definite reaction on the part of the fisher. The change in rhythm and the extra tracks tell us that the fisher was very interested in the coyote trail.

Parsing out all those extra tracks is tricky, but you can see my interpretation of the encounter in the next photo, a close-up in which I’ve labelled the tracks. The coyote trail is a nearly straight sequence of tracks on a rough diagonal from lower left to upper right, and its tracks are marked as CL F+H, CR F+H, etc. The fisher tracks are labelled RH, LH etc. Starting at the lower right there’s a right rear track from the fisher’s loping approach, and to the left of that track there’s a group of five prints. Four of those tracks make up a shortened lope pattern and the fifth sits above them and points toward the eventual continuation of the fisher’s journey. The tracks closest to the coyote trail show how the fisher paused and did a thorough examination. Apparently satisfied with its inspection, the fisher continued loping in the original direction.

Why was the fisher so interested in the coyote trail? A coyote would represent a danger to a fisher. A fight between the two could cause the fisher’s death and also pose needless risk for the coyote. But encounters between predators rarely happen because they keep tabs on each other’s movements. The tracks would have revealed the identity and nearness of the coyote, and the fisher apparently decided that it wasn’t in any danger.

I found the coyote tracks in the next photo on a sunny morning following an overnight snowfall. I must have been there not long after the coyote came through, since its tracks didn’t show any signs of melting. The coyote walked from right to left, changing its direction as it crossed an otter trail (which also showed no signs of melting) but otherwise taking little notice of the mustelid’s slide.

I continued to follow the coyote trail and soon came upon a spot (shown in the next photo) where the animal had encountered several pheasant trails. The pheasants had been there earlier in the morning before the sun had risen above the distant trees. The snow would have been several inches deeper, and the pheasants would have dragged their feet through it. Once the sun rose higher it began to melt the snow. By the time I came along the depth of the snow had been reduced and the pheasant tracks had been transformed into a series of pits connected by a raised, wavy ridge. How did this happen? Disturbances created by footfalls create slightly denser snow around–and between, if the feet drag–tracks, and denser snow melts more slowly than undisturbed snow. The compacted snow around and between the pheasant prints sank down more slowly and was transformed into the raised ridge. The coyote came along shortly before my passage, so its tracks hadn’t been exposed to the sun for very long and were unaltered. As the coyote investigated the pheasant tracks it left a jumble of prints, but it probably decided the birds were already far away and not worth pursuing.

So why did the coyote react differently to the two trails it crossed? The otter trail was more recent, judging by the lack of alteration, but a powerful animal like an otter would not have been seen as potential prey by a coyote. A pheasant, on the other hand, would provide a welcome meal for a hungry predator.

Signs of interaction when creatures cross paths may not be as obvious as the examples I’ve described above. You might just see a lighter track a little to the side, made as an animal paused before continuing on. Or differences in speed or gait may reveal an awareness of the recent presence of another creature. Whatever the reaction, it will always be transmitted through the animal’s feet and written in its tracks. Reading those tracks opens a window into the life of that animal.

Beavers at Work

Some animals live among us almost undetected, and others leave evidence that is obvious and long-lasting. Beavers are a good example of the latter, leaving signs of feeding on woody plants and creating dams and lodges that may last for years. The featured photo shows a lodge made of mud and sticks and surrounded by protective moat of water. What we can’t see is the underwater entrance which leads upward to a dry, multi-level living area. In the upper left quadrant of the photo there’s a dam, seen from the upstream side. The freshly peeled sticks that decorate the lodge and the dam, and the water lapping right up to the top of the dam, indicate that there were beavers in residence when the photo was taken.

Beaver dams can be impressive structures. The next photo is a view of a dam from the downstream side. The heaped up sticks conceal inner layers of mud interlaced with more sticks. Beavers react to the sound of flowing water, and any leaks are plugged with mud and more sticks. As long as the dam is maintained, the water level stays high enough to keep the lodge (not seen in this photo) secure in its watery surroundings.

A little exploration around the edges of an active beaver colony will turn up additional signs. When whole trees are removed the only thing left may be a chewed stump like the one below. Wood chips scattered nearby show where branches were removed and the trunk was sectioned and dragged off.

Some logs may remain where they fell, but they seldom go unused. One such log is shown in the next photo, and it’s a nice demonstration of the beaver’s chewing technique. The horizontal row of small cuts along the edge of the bark shows where the upper incisors were anchored. The vertical grooves in the lower peeled part of the log were made as the lower incisors were drawn up toward the anchored upper incisors. And why all this chewing? To get at the living cambium cells, located between the wood and the outer bark. Although there are exceptional cases where other food is available (such as the rhizomes of water lilies), most beavers depend on the cambium of woody plants for survival when leafy vegetation isn’t available.

Many dams and lodges are used for several years in succession, and newly added sticks and branches stand out against the mud and older sticks. The residents of a beaver colony also create deliberate messages indicating their claim to the location. In the photo below you see mud that was dredged up from the bottom and deposited on top of a grass hummock to create a scent mound. Whatever is handy at the edge of the pond, whether it be mud, muck, or rotting vegetation, can be dredged up and carried to the shore to make a pile. The final touch comes when the beaver drags its anus over the mound and deposits urine and secretions from its anal glands and castor sacs. The smell is not unpleasant, but it’s hard to describe. It reminds me of a horse barn, but it has also been compared to musk, human sweat, cheese, fruit, leather, birch beer, or some combination thereof. Scent mounds are most often created in spring, and the distinctive odor can persist for weeks.

If ponds and small streams aren’t available, beavers take up residence in creeks and rivers. But these habitats are subject to regular flooding, and the volume of flow during high water would destroy dams and lodges, so river beavers make their homes in the stream banks, digging underwater entrances and excavating living spaces above water level. If beavers are living in a river you may find peeled sticks, cut stumps, and scent mounds along the riparian margin. Another good clue is tracks in silty or muddy stream margins.

The tracks in the photo below were made by a beaver walking from lower right to upper left. The large hind prints make a wide zig-zag, starting with the left rear in the lower right corner. As in other four-footed walking trails, there are two footfalls–a front and a rear from the same side–at each zig or zag, but the front prints are mostly covered by the larger rear prints. All, that is, except for the two tracks at the upper left. The larger print above is the right rear, and next to it, just below, is the much smaller right front. Some of the rear prints may remind you of the tracks of a large bird. That’s because beavers often touch down lightly or not at all with their two inside toes, so the outer three toes make the most prominent impressions. But the heel marks behind the toes (as well as the wide palm areas at the bases of the toes) tell us it was a beaver, not a bird.

Whether they’re pond beavers or river beavers, at some point the animals will have exhausted the local food supply and will be forced to relocate to a better situation. If dams and lodges are not maintained water levels will fall. Chewed stumps and peeled sticks will weather to dull gray. Even though they aren’t fresh, these signs will persist and provide clues to the past presence of beavers.

But an abandoned beaver pond can offer its own discoveries. The amount of material amassed to form a dam or a lodge can only be appreciated after the water is drained. The exposed mud can be a great place to find the tracks of other creatures. And old beaver ponds provide great opportunities to find beaver scat. The animals normally defecate in the water, so seeing fresh scat is rare. But once the water has drained out, scats may be left on the sloping inner sides of the dam and the perimeter of the pond. Beaver scat is oblong and can be anywhere from 1/2 to 1 1/4 inches in length. The fibrous content is easy to see in the photo below–a beaver needs to chew through lots of bark and wood to get enough nutrition.

I never get tired of visiting beaver sites, because there’s always something new to discover. Whether it’s the prodigious size of a felled tree, the clever way the animals engineer channels to make transporting logs easier, or a muddy stream margin decorated with the tracks of beavers commuting to and from work, it’s always fascinating. Beavers lead complex lives and show great ingenuity in dealing with their surroundings, and the signs they leave can give us a window into their cleverness and adaptability.

Bears on the Move

[A note about last month’s post: you may have gotten a belated notification of the June blog; if so, my apologies. I had some trouble with my website, and the messages didn’t go out until the problem was fixed.]

Imagine you’re hiking on a sandy forest road, checking all the good spots for tracks. Suddenly you’re surprised to see what appear to be the barefoot tracks of a person. Could someone have been walking around way out here without shoes on? But as you look again, you realize that there’s something odd about the prints. Instead of the big toe being on the inside of the foot, it’s the outside toes which are larger and positioned farther forward. In fact, the big toe isn’t really very big. And ahead of each toe there’s the unmistakable mark of a claw. These tracks belong to a different creature altogether–a bear.

The black bear (the only bear we have in the east) that made the tracks above was moving at an indirect register walk, placing each rear foot on the spot just vacated by the front foot from the same side. The zig-zag pattern matches the pattern made by a walking person, but it’s a messy zig-zag because the coverage of the front prints by the hind ones isn’t precise. That’s a sure clue that the trail was made by a four-footed creature.

Another kind of movement often used by bears is the overstep walk, a gait in which the rear foot comes down just ahead of the front foot on the same side. In the next photo a bear moved from bottom to top at an overstep walk, leaving a sequence of tracks made up of sets of two. Each set is composed of a hind track trailed by a front track, and the pairs of tracks are arranged in the familiar zig-zag of a walking gait. Starting from the bottom, the sequence of tracks is: left front, left rear, right front, right rear, left front, left rear.

In the next image you see a left front and a left rear print taken from an overstep walk sequence. The direction of travel is toward the right, and the rear print with its fully impressed heel looks larger–and more human–than the heel-less front track behind it. In both front and rear tracks the outer toe (the upper one) is slightly larger than the others, but compared to human tracks the difference in size is less pronounced. The inner toes shows nicely in both tracks, and they’re distinctly smaller than the rest. There are a few claw marks, but they’re not easy to find because they’re not exactly in front of the corresponding toes.

Bears are classified as plantigrade creatures, meaning that their heels often touch the ground when they are moving at a normal walk. I’m hedging a bit here because heel registration in bears is variable. Rear tracks may show complete and well connected heels, as in the photo above, or partial heel impressions as in the upper sets of tracks in the preceding photo. And if you look at the first photo you’ll see heel marks that are separated from the middle pads by ridges.

Front prints commonly lack heel impressions, but there are times when the full length of the front foot, from heel to toes, does register in the track. The right front track in the next photo (direction of travel toward the left) is a good illustration. The middle pad forms a broad, slightly curved depression in the center of the photo. To the left the four largest toes and their claws show as clear imprints, but the smaller fifth toe (which would have been toward the bottom of the photo) didn’t touch firmly enough to register. To the right of the middle pad there’s a separated circular impression made by the heel pad.

Female bears which bore young over the winter are now travelling with their offspring and leaving tracks like the ones in the next photo. At the lower left you can see the mother’s print. The more delicate prints of the cub, with their prominent claws, are above and to the right. Young bears are active and playful, but they are also vulnerable to predation by coyotes, bobcats, and even adult male bears. Those sharp claws allow cubs to climb to safe refuges high in trees.

Bears are constantly on the move to access a variety of seasonally abundant food sources, often travelling miles as wild fruits and nuts ripen, colonial insects become available, or crop plants mature. Wherever they cross silt beds, sandbars, muddy forest roads, or other trackable surfaces they may leave prints for us to find. So when you find tracks that bear an uncanny resemblance to human tracks, look again. You may be on the trail of a roaming bruin.

The Precarious Lives of Fawns

Can you see what lies almost hidden in the first photo? At the very center of the frame there’s a bit of bright chestnut color that doesn’t match the faded leaf litter around it. This spot is in a hedgerow that I often pass by when I walk my dog, and that’s what I was doing a few weeks ago when I saw that patch of incongruous brightness. I immediately moved away and headed for home, and my dog never seemed to realize the fawn was there. I returned, sans canine, and carefully approached to take some pictures. The fawn’s spotted coat and bright chestnut color didn’t blend very well with the ground or the green leaves, but its stillness and lack of scent were effective–at least for my dog. When danger is near a fawn’s heart rate and breathing actually slow down, making it even more undetectable.

Very young fawns spend most of their time lying hidden while their mothers forage and rest in separate locations, but this was a surprising place for a doe to leave her fawn. The hedgerow is not far from several village streets and it lies between grass lawns that are mowed regularly. But contrary to what you might think, this closeness to human activity may actually be beneficial. The survival rate for newborn fawns is low–perhaps 50% or less in the first few weeks of life. Any wild hunter that comes close enough to detect a resting fawn will take advantage of the easy meal. For animals like bears, which struggle to find enough nourishing food in early summer, a fawn is a nutritional bonanza. As it lay in the hedgerow, the risk to the fawn from humans and dogs (mostly on leashes) may have been offset by the reluctance of coyotes and other predators to forage in such areas.

Fawns gain strength rapidly, and in a few weeks they begin to move around. The young ones are soon accompanying the does wherever they go, and that’s when we start finding their tracks. Generally the first ones we see are about one inch in length, noticeably smaller than their mothers’ tracks.

But sometimes an even younger fawn leaves visible tracks. In the photo below a housecat print lies on the left, facing to the left, and a fawn track lies on the right, facing right. The cat track was only 1 1/2 inches wide and the fawn print was not quite 3/4 inch long. That’s the smallest fawn print I’ve ever found.

At first does and their fawns move slowly and keep to themselves. As the young ones grow larger they begin to travel more, and family groups may join together in small herds. The photo below shows the tracks of a fawn walking beside its mother.

The hooves of fawns are small copies of the hooves of adult deer, but they don’t show the wear that is characteristic of the hooves of the grownups. In the photo below you see a fawn’s left rear foot. Although this fawn still had a spotted coat, it was old enough that it would have been making limited movements with its mother. But even with its increasing mobility it fell prey to a predator, probably a coyote.

In the next photo you see the tracks of a fawn galloping (or more accurately, bounding) from bottom to top. At first glance the track group may look ordinary, but there’s something unusual about it. The sequence of prints, starting at the bottom, is right front, left rear, left front, right rear. Normally in this kind of movement we would expect the two hind prints to fall outside of the two front prints, but instead the left hind track is just inside that of the left front. It’s as if the left back leg were going to pass to the inside of the left front leg instead of to the outside. You’ve probably seen playing kittens or puppies take on strange positions, and fawns are no different. Their flexible bodies can do things that we don’t often see in adults.

Just as for other animals, play serves a serious function, preparing the fawns for a future that brings all sorts of challenges and dangers. Along with bouts of play, fawns are busy imitating their mothers and absorbing other knowledge: good areas to forage and bed down, escape routes, communication with other deer, and a multitude of other skills that they’ll need as adults. The first three months are the most precarious period of their lives, and once they’ve survived that long, juvenile deer have a much better chance of survival.

Separating Felines and Canines

Cats and dogs–they live among us as companion animals, and their wild relatives are a familiar presence in our landscapes. The two groups differ from most other mammals in having four toes on both front and back feet, and in both groups there’s a smooth pad (the middle pad) behind the toes. So how to tell them apart? One thing we often hear is that canine tracks show claws and feline tracks don’t, but the presence or absence of claws can’t always be relied on. Cats can extend their claws if they need more grip, and the claws of wild canines may not touch the ground because they are naturally trimmed by constant movement. Fortunately there are other features that can help us to distinguish between canines and felines. It’s a simple matter of paying attention to details, and there are plenty of them. So let’s get started.

In the photo below you see the front track of a coyote, direction of travel from bottom to top. The overall shape is elongated, the toes are relatively large compared to the middle pad, and the outer toes are tucked tightly behind the leading toes. The middle pad has a pointed forward edge. Roughly in the center, between the toes and the middle pad, there’s a dome-like area, and an X is formed by the ridges between the middle pad, the outer toes, and the two leading toes taken together. The dome and the X are the negative spaces, areas that are not pressed down by toes or pads, and their arrangement is an unmistakable indicator for members of the dog family. (By the way, note that there are no claw marks.) And another important detail: the track is symmetrical. By symmetrical I mean that the right half is almost identical to the left half.

Here’s a way to grasp the concept of symmetry. In the next illustration I’ve added a vertical line which bisects the track. If you imagine folding the right half over along the line so it lies on top of the left half, the two halves will match almost exactly. The two leading toes are almost even with each other, the inner and outer toes are of similar size and spacing, and the middle pad seems to point straight ahead.

Now let’s compare a feline print. The photo below shows the front track of a bobcat. The overall shape is more rounded, the toes are relatively small compared to the middle pad, and they’re arranged in a wide arc in front of the middle pad. The left-most toe is smaller and farther back than the others. There’s no central dome, and the ridge between the middle pad and the toes is broadly curved or C shaped. Rather than pointing straight ahead, the middle pad is canted to the left. The arrangement of toes and middle pad makes the track very asymmetrical.

To get at the asymmetry here’s the same photo with a vertical line bisecting the track. If you do the mental experiment of folding one side over onto the other as we did with the coyote print, you’ll see that the two halves don’t match. One toe leads all the others, and the smallest one lags behind the other three. The whole print seems to be canted to one side. Because it’s asymmetrical we can tell which front print this is–it’s the left. If we were looking at an isolated coyote track it wouldn’t be possible to know if it was a left or a right.

Here’s the front print of another canine, a red fox. It’s not as elongated as the coyote print, but the overall shape is still more oval than round, and the outer toes are tucked in behind the leading toes. The central dome and canine X are unmistakable, and the track is beautifully symmetrical. In this case claw imprints show as delicate punctures directly ahead of the toes. The mud was just moist enough to show the hair on the underside of the foot and the chevron in the middle pad perfectly.

Perhaps you’re thinking that I oriented the bobcat track incorrectly, and that if it were rotated a little it could be made to look more symmetrical. But the asymmetry is inescapable, no matter how you look at it. In fact, when an animal is moving at a steady gait the correct orientation of each print is dictated by the direction of travel, and the imaginary bisecting line should be parallel to the direction of travel. The next photo shows part of a sequence of tracks made by a house cat moving at an overstep walk, a gait in which the rear print lies ahead of the front print from the same side. The direction of travel is from lower right to upper left.

In the next illustration I’ve added a line which defines the direction of travel to the same photo. (Sorry about the slight wobble, just imagine it’s really straight.) With the line as a reference, you can see that each track is canted to the outside. Also notable in this photo are the shapes of the middle pads: wide and blunt on the forward edges and scalloped on the trailing edges. The C-shaped ridges between the middle pads and the toes are especially striking.

The topic of gaits brings up another criterion sometimes said to distinguish canines from felines–direct register versus indirect register. Walking felines are said to place their feet in direct register, so that the back foot comes down exactly on top of the print of the front foot from the same side. Canines are supposed to prefer the indirect register walk, placing the back foot partly, but not exactly, on top of the front from the same side. But this isn’t a make-or-break test. The next three photos illustrate this point: first you see a bobcat direct register walk, next a bobcat indirect register walk, and finally a red fox direct register walk. The fact is that both felines and canines use both direct and indirect register walks. It’s fair to say that domestic dogs and cats are more likely to walk in indirect register than wild canines, but even among wild species there’s variation, and the difference isn’t very useful for identification purposes. And of course it wouldn’t apply in other kinds of walks, such as the overstep walk in the previous illustration.

Our other fox, the gray fox, makes tracks that are a little more catlike. In the photo below you see a rear print, below, and a front print, above. The overall shapes are round enough to be confusing, the central dome and canine X are a little different from the ones shown for the fox and the coyote, and in the hind track there appears to be a leading toe. Gray foxes have semi-retractable claws which don’t usually show in tracks, so the presence of claw marks suggests that the animal needed more stability in the wet mud.

In spite of the variations the tracks are clearly canine. Compare them to the bobcat tracks in the next photo, this time a left rear below and a right front above.

These two photos bring out some potential pitfalls in the task of differentiating canines from felines. Animal feet aren’t rigid, and toes may spread or tighten depending on the animal’s movement and the nature of the substrate. In the gray fox hind print the two leading toes gripped the soil differently, causing one to appear farther ahead than the other. The normal symmetry of canine tracks can be altered by head turns, changes of direction, or by sloping terrain. Another potential source of uncertainty is the fact the hind feet of felines are often more elongated than the front feet. In the bobcat photo above the rear track has a slightly canine appearance due to the tighter arrangement of toes and the more oblong shape.

And lastly, never underestimate the power of domestic dog tracks to create confusion. The track in the next photo was about the size and overall shape of a bobcat print, lacked claw marks, and mimicked the blunt middle pad and C-shaped ridge of a feline. Red flags were raised by the symmetrical structure and the large toes, but it was really the presence of more tracks which clinched the identity as dog. Domestic canines are incredibly variable–their tracks can be quite round and the tendency of the toes and middle pads to spread can give the negative spaces a feline appearance.

So the task of separating canines and felines is not always easy. Isolated prints are harder than more complete sequences, and weathering and distortions can make things difficult. But the more you study them, the better you’ll be at picking out the crucial features. And if one of these creatures is rare in your area, it’s a joy to find it’s tracks and know you’ve made a solid identification.

When the Snow Gets Deep

One of the challenges in a winter like the one we’ve been having is tracking in deep snow. Our native animals are mostly well equipped to cope with such conditions, but the evidence they leave can be mystifying–animals may change their habits, tracks and trails may look very different, and the details we generally rely on for identification may be absent. But the lives of animals are still written in the snow. To read these stories we just need to acquire some new reference images and expand our tracking skills.

A red fox made the trail shown below. In the deep snow the direct register walk was the most energy efficient gait, each hind foot coming down in the hole made by the front foot on the same side. Compared to walks in easier conditions the fox’s steps were shorter and its trail width was greater. The animal lifted its feet cleanly out of the snow, leaving just a few drag marks.

The direction of travel, from bottom to top, is revealed by the sprays of snow which fell off the feet as they rose out of the holes and moved forward. Whether animals are walking or moving at faster gaits–as long as their movements are regular and smooth–snow falling from their feet usually lands ahead of the tracks. Only during sudden acceleration or changes of direction do we see snow pushed backward or to the side.

A coyote walking from left to right made the trail in the next photo. The snow was less consolidated so there’s a softer appearance to the trail. The details in the track floors are obscured by the snow that fell in as the feet were lifted out, and the animal’s feet skimmed the soft surface leaving drag marks. Looking down into the holes (which is always a good idea in this kind of situation) we can see the shapes of the forward edges of the animal’s feet. The overall shape of a coyote’s foot is oval or egg-shaped, but how should we describe just the front half? The best I could come up with is parabolic or bluntly arched. Whether or not there’s a word for it, this shape is characteristic of coyotes and red foxes, and also some dogs. And there’s another feature that is typically canine: in the very tip of the hole on the right you can see two small dents made by the leading claws–a dead giveaway for a red fox or coyote. Gray foxes usually have more rounded leading edges and less tendency to show claw marks. Being shorter legged than red foxes, gray foxes are more likely to leave drag marks, and dogs are also prone to dragging their feet.

These two trails illustrate the general appearance of canine trails in deep snow. Because walks in deep snow tend to be very close to direct register it may be possible to get rough measurements for track widths, and this, plus stride or step length, can help to separate coyotes from red and gray foxes.

Bobcat trails in deep snow may be quite different from canine trails. In the photo below a bobcat walked from bottom to top, and at each step it spread its feet as they went down into the snow, creating a sequence of interlocking triangles. As usual, snow obscured the details of toes and pads at the bottoms of the holes, but in the lowermost impression you can see that the forward edge of the track is widely crescent-shaped rather than parabolic.

Sometimes animals negotiating deep snow move faster, perhaps out of fear or maybe just playful antics. In the photo below a red fox bounded from upper left to lower right, leaving holes where its body went in up to its shoulders. There may not be much information inside the holes, especially if the snow is loose and movable as it was when the photo was taken, but their width provides a rough measure of the width of the animal’s body. The level of effort required for this kind of movement means that it can’t be sustained for long periods, so following the trail either backwards of forward will probably bring you to a change of gait.

In spite of their long legs, deer are not well suited for moving in deep snow. Their feet are small in proportion to their body weight, so they sink in deeply. Deep drag marks like those in the photo below are typical, and sometimes the tips of the toes can be seen at the bottoms of the holes.

In deep snow deer may limit their movements to trails they’ve already made, such as the one in the next photo, where they can move with less effort. If the difficult conditions persist the animals may limit their movements to very restricted areas which become crisscrossed with trails. These deer yards are usually found under conifers, where the snow isn’t as deep and the evergreen foliage traps heat. When deer yard up the available browse is quickly eaten, so they eat very little, reduce their activity, and wait out the winter.

For short-legged animals like porcupines, skunks, and muskrats the only option in deep snow is to bulldoze their way through. In the photo below a skunk struggled from upper left to lower right, its body plowing through the snow and its feet punching deep holes in the bottom of the groove. The small pits made by the feet, combined with the short strides and wide trail width are good indicators of the animal’s identity.

When temperatures fluctuate or sun melts the surface, snow can develop an icy crust. Sometimes this reduces the problem of movement, allowing lighter animals to move easily over the surface. But if the hardness of the crust varies or the animal is just a little too heavy, we may find scenes like the one in the photo below. A coyote attempting to cross a drift found that it wasn’t always supported by the crust. Where it broke through it left crisp outlines of its lower legs and spread toes.

Like other animals, rabbits and squirrels can plunge deeply into snow, and this can make it hard to identify their tracks. But the difference in the positioning of the front feet usually provides a clue to the animal’s identity. The next photo shows a cavity made by a gray squirrel bounding from lower left to upper right. Inside the hole there are two depressions, each one made by a front foot and a rear foot from the same side. The wide separation of the depressions and the equally wide entry and exit disturbances give the hole a boxy or rectangular shape.

Compare that to the next photo of a rabbit in deep snow, also bounding from lower left to upper right. Because the rabbit brought its front feet down on or close to the center line of the trail, the entry point (at the lower left) is narrow. The rear feet made a wide depression in the deepest part of the hole and left separated drag marks coming out. The result is a triangular cavity with the wide end opening toward the direction of travel.

Maybe the biggest hinderance to learning how animals move in deep snow is just getting out into the stuff. You’ll need snowshoes or skis, or at the very least good gaiters, to get close to the tracks. But if you spend some extra time arranging all your gear you’ll be rewarded with a deep look into the lives of animals in deep snow.

Fisher Frolics

After a long absence fishers have returned to our northeastern forests and made themselves completely at home. These medium-sized members of the mustelid family can travel miles in a single day at their habitual loping gait, shown in the photo below (direction of travel toward the upper right). At the lower left you see four separate prints; the sequence, starting at the left, is left front, left rear, right front, right rear. The next set is also made up of four prints, but it looks like just three because the left rear fell mostly on top of the right front. By the way, the arrangement you see on the ground is not the same as the order of footfalls, which is left front, right front, left rear, right rear for both groupings.

The addition of fishers is a benefit for our ecosystems, but aside from that, having fishers in the woods makes for some interesting tracking. If you follow fisher trails you may come upon spots, such as the piece of wood in the next photo, where the snow has been strangely disturbed and smoothed. A fisher came in from the left and rubbed its belly over the wood, depositing chemical signals from the scent glands in its skin. Fishers usually choose protruding objects for marking, and the process can involve some amazing bodily gyrations. Rubs are sometimes topped off with a little urine or scat, and the finished creations serve to communicate territorial claims or availability to potential mates.

Fishers are drawn to trees, and when travelling they often move from one tree to the next to investigate for the presence of squirrels, one of their principal prey items. So it’s no accident that the fisher that made the trail below headed directly to a tree. The animal was travelling at a double-register bound, leaving a string of paired impressions separated by relatively long spaces. A bounding fisher covers the spaces between tracks in graceful arcs and lands on its front feet almost, but not quite, simultaneously. As it lands it draws its body into a tighter curve, and the front feet lift off just as the hind feet come in to land where the front feet were. The animal then takes off from its hind feet in another arcing leap. By bringing the hind feet into the same holes made by the front feet the fisher conserves its energy when travelling in deep snow. Note that one of the impressions leads the other, and that the two hollows are close together and relatively large. Squirrels, and most other animals, also alter their gaits in deep snow for more efficient movement. If a squirrel had bounded toward the same tree its trail would also be a sequence of double impressions, but each hollow would be smaller and the two would be mostly even with each other and more widely separated.

Fishers are expert hunters. It’s rare to find a kill site, but it’s not uncommon to find a trail that reveals a successful hunt. In the photo below the prints of a bounding fisher go from left to right across the middle of the frame. Above each group of tracks you can see a slightly curved line carved into the snow. The fisher was carrying a prey animal in its mouth, probably gripping the back of its victim. Something dangling to the side, a foot or an ear, brushed the snow each time the fisher landed. Such marks can fall outside the trail or within it, but they always occur at regular intervals in synchrony with the predator’s gait. Random gouges made by wind-blown leaves or other objects may fall in or near a trail, but they don’t repeat in synchrony with the track groups the way the marks of a prey item being transported do.

Winter is mating season for fishers, and when a male and female come together the story is recorded in the snow. If you come across a wild-looking collection of tracks like those in the photo below check for size differences. Male fishers are generally almost twice as large as females, and their tracks reflect their greater size. In the photo, male and female tracks are mixed together near the tree, but the smaller tracks of the female can be seen by themselves at the lower left. This female was probably receptive (not always the case) because their prints were mixed together over a wide area.

Looking carefully I found some nice prints, shown in the next photo, which showed the size difference. A small female track lies to the left of a much larger male track, both heading from left to right.

I’ve already mentioned the fisher’s affinity for trees. The animals are excellent climbers, able to scale vertical tree trunks to get into hollows sheltering squirrel nests or attack porcupines clinging to upper branches. A fisher’s rear feet can rotate 180 degrees, allowing it to grip with its rear claws when descending head-first. You may find fisher trails that lead to and end at trees the way squirrel trails often do. And sometimes, if the snow is deep and soft, you might find a place where a fisher skipped the downward climb and leapt from the tree trunk. In the photo below a fisher jumped from a tree outside the frame at the upper right and landed in the upper right quadrant. There’s a rectangular hole made by the fisher’s body with four pits at the corners made by its four legs. To the right of the hole its tail made a curved gouge. Its first bound can be seen in the lower left quadrant.

When trailing fishers you might have to keep at it for a while–it’s amazing how much distance the animals can cover in a single hunting or mate seeking episode. But if you’re persistent you’ll be rewarded with fascinating evidence of of their daily activities.

Sorting Out the Small Rodents

Rodents are considered one of the most successful groups of mammals, so it’s not surprising that the northeast hosts many different kinds. They range in size from the tiny woodland vole (weighing an ounce or less) to the beaver (50 pounds or more). The small ones dominate, both in abundance and in their potential to confuse. Most of these little creatures are active in winter, so it’s a perfect time to get a handle on their distinguishing features.

The photo below shows a set of prints made by a red squirrel bounding from left to right. The five-toed rear tracks are nearly even with each other and set widely, their three middle toes parallel and their inner and outer toes diverging. The four-toed front tracks are set more narrowly and staggered, and their four toes are slightly splayed. Behind the toe impressions, the middle pads of both front and rear feet (analogous to the bumps over the knuckle joints in your palm and the ball of your foot) appear as clear indentations. The heel pads of the front tracks (like the heel of your hand) show in both right and left front prints, and the heel area of the right rear track (analogous to the heel of your foot) is a smooth elongation behind the middle pads.

Here’s a chipmunk group of four, with the direction of travel this time toward the top. The left front and rear tracks are partly superimposed, but the similarity to the tracks in the first photo is plain to see. This is what I call the rodent foot plan, and once you absorb it you’ll recognize it in other small rodents, including squirrels, chipmunks, mice, and voles.

But there are some variations which–if available–can be important in pinpointing an identification. The photo below came from the bounding trail of a southern flying squirrel, an animal similar to a chipmunk in body size (although lighter in weight). Compare the middle pads in the right rear tracks (the farthest to the right in each photo): in the chipmunk they’re well separated and form a sharp curve. The middle pads of the flying squirrel are closer together and form a gentle crescent.

If your reaction to that is, ‘you’ve got to be kidding!’ you’re not far off base. It’s a real difference, but snow conditions are rarely perfect enough to see that kind of detail. So how often can we be sure which small rodent made the tracks we’re seeing? Quite often, it turns out, because we have two additional diagnostic tools: trail width and habitual movement patterns. The tracks in the photo below, a white-footed mouse bounding toward the upper right and a gray squirrel bounding toward the lower right, are similar arrangements but are vastly different in size. In this case it’s easy to know which is which, but for less obvious differences, such as red squirrel versus gray squirrel, measurement of the overall width of the pattern, known as the trail width, can really help.

To measure the trail width of a bounding animal, imagine or mark lines parallel to the direction of travel which touch the outermost parts of the two rear tracks. Below you’ll see the same photo with lines delimiting the trail widths. Next, measure the distance between the two lines. The nice thing about this is that the trail widths of our most common small rodents fall into a simple size progression. In inches, trail widths for white-footed and deer mice measure 1 1/4-1 3/4; chipmunks, 1/1/2-2 3/4; red squirrels, 3-4 1/2; and gray squirrels, 4-6. At 1 3/4-3 inches the trail width for southern flying squirrels is similar to that of chipmunks, and northern flying squirrels, at 2 3/4-4 1/4 inches, overlap on the low side with red squirrels. Although trail width can be determined for any gait, the bounding gait so common in small rodents is especially suited to this measurement.

Habitual movement patterns are another useful tool for identifying small rodents. In the next photo a gray squirrel bounded at a good clip from bottom to top, leaving groups of four prints separated by relatively long distances. In each group of four the landing tracks of the smaller front feet are behind the take-off tracks of the larger rear feet. Bounding trails of red squirrels and chipmunks are similar in overall proportions. It’s not that these animals always make long leaps. If they’re moving slowly the distances between the groups of four can be smaller, and the hind feet may not pass as far ahead of the front feet. Compare the arrangement of the gray squirrel prints in the previous photo with that of the slower moving red squirrel in the opening illustration. The point is that the habitual travelling movement of these animals creates trails with characteristic four-track groupings and relatively large spaces between groups.

Compare the pattern above to the next photo, the trail of a southern flying squirrel, bounding from lower right to upper left. In this trail the larger rear prints are behind the smaller front ones, and the distance between the groups of four is smaller. In the trails of northern flying squirrels the rear tracks are often ahead of the front, but both species of flying squirrels have sacrificed strength for lightness and aerodynamic design and are unable to match the long leaps of their non-gliding relatives.

Snow depth can affect the foot placement of bounding rodents. To the white-footed mouse that made the tracks in the photo below the snow was fairly deep, so the groups of four are reduced to sets of two, each of the paired impressions made by sequential impacts of front and rear feet from the same side. All of the rodents I’ve been discussing do this when deep snow makes it more energy efficient. But even in these reduced patterns trail width can still be measured, as long as we make sure we’re looking at the actual tracks and not the larger openings around them. And like squirrels and chipmunks, mice make shorter leaps when moving less energetically. An example of mouse trails with consistently shorter leaps can be seen in the opening photo of last month’s article.

Meadow voles are chunkier and have shorter legs than white-footed mice, so they can’t make long leaps, but their trails are roughly as wide as those of mice. It’s not always easy to tell whether a bounding trail with short leaps was made by a vole or a mouse, but if the trail goes on long enough differences usually show up. A vole’s foot placement is rarely as even and foursquare as that of a mouse, and voles tend to make frequent shifts in gaits. It’s not unusual for an individual vole trail to vary among lopes, bounds, trots, overstep walks, and scurrying gaits that are difficult to categorize. In the next photo there’s a partly roofed vole tunnel meandering between the lower right and the top center. A vole traveled from the left side of the frame toward the tunnel in a bounding gait, with typical short leaps and uneven foot placement. The thin line in the center of the trail was made by the tail.

If you’ve made it this far in this treatise, you may feel like your brain is reeling. Believe it or not, I had to leave out many details, and I haven’t even addressed the issue of distinguishing small rodents from other small mammals. The important thing is to get started. Every time you work through a small rodent puzzle you’ll learn more. So be patient and persistent, and enjoy the eureka! moments when a few puzzle pieces fit together to form part of the larger picture.

What’s Underfoot Makes All the Difference

I’ve been finding lots of coyote tracks lately, and as I go back over my photos I’m amazed at how different they can look from one another. It’s not that the substrates are radically different–just sand, silt, or mud. And to make my point I’ve narrowed down the gaits to just walks and trots. But still, no two tracks are alike. How can what seem like small differences in conditions give tracks such strikingly different appearances?

Moist, dense sand captured the tracks of a trotting coyote shown below, a front at the lower left and a rear at the upper right. The animal’s feet sank in just enough to show lots of details: the difference in size between the front and rear prints, the compact positioning of the toes, the greater depth toward the tips, and the alignment of the claws straight ahead. Both middle pads show only lightly, and the smaller pad of the rear print can barely be seen. In the front track there are small clumps of sand in the two leading toe impressions that were tossed there by the claws when the foot was lifted.

But all sand is not the same. In the photo below of a front print (for the sake of comparison I’ll stick with front prints for the remainder of this article), partial drying resulted in dark toe and middle pad impressions surrounded by lighter dry sand. I suspect that the sand was uniformly wet when the track was made. If the sand around the perimeter of the track had been dry when the coyote’s foot impacted, it would have lost its coherence and crumbled or flowed outwards. Instead pressure from the toes formed plates and fissures (known to trackers as pressure releases). Since nothing disturbed the track before I found it later that morning, these formations dried without disintegrating (although part of the ridge between the two leading toes did fall to the side).

In addition to the larger areas of dry sand there are tiny, light colored squiggles in the floors of the toe and middle pad impressions. These also indicate that the sand was wetter when the track was made; small bits of wet sand adhered to the coyote’s toes and middle pads (dry sand doesn’t do this), and came up as the foot was lifted. Being slightly elevated and also less dense, these particles dried faster than the packed floor of the track. You can see the same thing at an earlier stage of drying in the first image.

This kind of partial drying can often tell us how long ago a track was made. Dew creates wet soil surfaces, so tracks made early in the morning in substrates subjected to dew-fall look uniformly moist immediately after they are made. But on dry summer days the elevated parts begin to lose moisture quickly, and lighter colored halos form around the darker depressed parts of a track. As the substrate continues to dry the entire surface becomes lighter in color and the structure in the cracks and plates disintegrates, resulting in a track with softer edges and uniformly lighter color. Another round of dew-fall and daytime drying may reproduce the halo effect, but the softer edges usually give away the greater age.

The track shown below was made in dry sand, and any structure that existed within the sand disappeared with the impact of the coyote’s foot. Instead of forming plates and cracks in response to the pressure of the foot, the sand moved more like a liquid, producing soft outlines and rounded pressure releases. Although some detail was lost, the compact form of the foot and the triangular shape of the middle pad are still evident. If this track was moistened by dew-fall the night after it was made, it would look wet early the next morning and would develop a lighter colored halo as drying progressed. But the rounded edges would show that it was made at least a day earlier, when the sand was dry.

The photo below shows what fine, moist mud can do to reveal track features. The toes and middle pad are crisply outlined and show very little disturbance, suggesting that it was made at a walk. In front of and behind the middle pad (and a bit at the sides of the toes) there are impressions of the hair which fills the spaces between and around the toes and middle pad–in November, when I found the print, the coat was already thickening ahead of the cold weather to come. We even see the slightly pebbled texture of the skin, especially in the middle pad. This beautifully detailed print illustrates several important diagnostic features of coyote tracks: the trim outline with tightly held, forward pointing toes; the lack of claw imprints telling of shaping through natural abrasion; and the outline of the middle pad with its triangular forward edge and lobed trailing edge.

You may wonder why particles of mud weren’t lifted from the floor of the track the way clumps of sand were in the first two examples. After all, mud is sticky, isn’t it? It certainly is, and the stickiness shows in the narrow ridges pulled in by the toes and the middle pad. This is especially obvious in the lower edge of the left leading toe, the back edge of the right outside toe, and the back edge of the middle pad. But mud is also very fine-grained and has greater internal coherence than sand, so it doesn’t pull apart as easily, especially after it is compressed by the weight of an animal’s foot.

In the next photo the silty mud was not as wet and was much firmer, so the track is shallower and the toes and middle pad look smaller. It’s not that this coyote actually had smaller toes. It’s rather that less of the toe and pad surfaces touched the mud. Think of holding a beach ball and pressing it into soft beach sand to make a large circular impression, then compare that with pressing the ball onto a sidewalk where the contact area is much smaller. The outer toes look especially small, and the lobed trailing part of the middle pad is narrower compared with the same area in the previous photo. Another striking feature is the disturbances in the toe impressions. Cracks and displaced sections in the forward parts of the toes show that the foot pressed backwards against the substrate. These and the tiny punctures made by the leading claws suggest that the animal was moving with more energy (perhaps at an overstep walk or trot) than the coyote that made the track in the previous photo.

Finally, here’s a slightly quirky example of the way tracks can come to have different appearances. I found the print shown below on a truck trail that had been surfaced with pulverized rock quarry tailings. The coyote had walked through a stretch covered with fine white rock dust before it crossed the dried mud in the photo. The dust adhered to its feet and was deposited on the mud to make light tracks on the darker background. As in the previous photo, the toes and middle pad are relatively small and separated by wide negative spaces, but the diagnostic features of a coyote print can still be seen.

There’s so much to learn from tracks: how the track was made, what the conditions were like at the time, how old the track is, and what happened after the animal passed by. We can even get glimpses of some of the challenges in the daily lives of animals. Understanding the subtle (or not so subtle) differences in the appearance of tracks can help us to delve deeper into the myriad messages tracks carry.

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.