snow tracking – Page 2 – Linda J. Spielman

Canine Romance

It may seem like the wild creatures are all hunkered down, just doing their best to stay alive and wait out the cold season. But for wild canines there’s more going on than simple survival. This is mating season for foxes and coyotes, and they’re engaging in behaviors that will eventually lead to reproduction. For human trackers the first clue to their new fixation is the increasing frequency of scent marking. In the photo below you see a splash of urine on the snow to the right of the corn stalk, left as a message to others of its kind by a gray fox.

Urine contains complicated combinations of chemicals that, to a discerning canid, reveal the identity and health status of the animal that produced it. As mating season progresses, changes in the chemical signature also indicate the animal’s readiness for mating and reproduction. Most of these messages are too subtle to be detected by people, but fox urine is an exception. The urine of both red and gray foxes takes on an increasingly musky, skunk-like odor as hormonal changes progress, and in late winter this odor is strong enough for a person to detect it a good distance away from the deposit.

The fox whose scent mark is seen in the image above was walking from the upper left to the lower right. We know that the it was a male because of the placement of the urine off to the side of the animal’s trail. The direction of travel is revealed by the appearance of the snow around the edges of the tracks. When a foot goes down into snow it pushes any movable material down into the hole. When the foot comes up and out again it often brings a little snow up with it, and this snow is dropped around the leading edge of the track as the foot moves forward above the surface. This means that the snow around the entry end of a track is relatively undisturbed while the surface at the exit end is decorated with sprays or scatterings of snow. In the photo of the gray fox trail there are four deep tracks, each one the landing place of a front and a rear from the same side, plus a light track near the third deep track. Starting at the upper left (and considering just the deep tracks), the sequence is left front + rear, right front + rear, left front + rear, right front + rear. The animal was standing on its right hind foot when it lifted its left hind leg to squirt urine at the corn stalk. The shallow print was probably made as the fox placed its right front foot lightly on the snow for balance while it was urinating. The corn stalk was a convenient object, but rocks, clumps of weeds, branches, or anything else that protruded above the snow would have done as well.

Among coyotes and foxes, early winter is the time for the establishment or reestablishment of pair bonds. Those that spent time apart after they raised a litter in the previous season usually rejoin, and unattached animals roam widely in search of potential mates. Bonded pairs establish their territory by scent marking around the edges, especially along borders shared with others of their species. Unless we are familiar with the area and the animals involved it’s hard to know whether scent marks are advertisements of availability or warnings that the territory is occupied.

During the lead-up to mating, pairs often travel together. The trails in the photo below were made by two red foxes travelling along a forest road. For at least half a mile the two trails wove back and forth, occasionally changing speed and sometimes diverging, but always coming back together. The male, with slightly larger tracks, enters the frame at a gallop, moving from the lower left to the upper right. The female is doing a side trot and her trail comes in at the lower right and leaves at the top of the frame just to the left of the male’s trail.

All of the behaviors I’ve described above help to strengthen the pair bond and propel the hormonal changes that lead up to mating. When the female’s endometrial lining begins to develop, her urine contains blood, and she leaves scent marks like the one in the photo below. She’ll soon go into heat and only then will she be receptive to the male’s advances.

The pair are both involved in the process of den selection and preparation, and pups are born about 50 (foxes) or 60 days (coyotes) after successful coupling. By initiating the early stages in the dead of winter nature insures that the pups are born in the spring when food will become increasingly abundant. Note: It’s important for trackers to avoid disturbing animals during this vulnerable time. We should not approach too closely or otherwise disturb a den site starting with the period of den preparation and continuing until the pups are no longer dependent on the den for safety.

This is, by the way, why coyote-dog hybrids aren’t as numerous as some people believe. Over thousands of years of domestication, dogs have lost the finely tuned sequence of reproductive behaviors that occurs in wild canines. Mating in dogs is no longer synchronized with the seasons, and males don’t assist in the raising of pups. Since these behaviors are genetically controlled, the offspring of matings between dogs and coyotes have disrupted patterns of behavior. The precise timing of reproduction is lost, as well as the strong pair-bonding and the dual effort from both parents (and sometimes female offspring from the previous year). For this reason the offspring of matings involving dog-coyote hybrids are unlikely to survive.

This is a great time of year to let tracking open a window into some of the underlying processes of the natural world. The mating rituals of wild canines have been shaped for success by natural selection, and this is beautifully illustrated in the behaviors we see in the tracks and trails of foxes and coyote.

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.

Dog Tracks: Common But Not Always Commonplace

Our familiar companion animals leave their tracks everywhere, and we see them so often we may find ourselves giving them only superficial attention. But if we look more carefully we may be surprised at how much they have to teach us. Dog tracks can show us the traits that are shared among dogs and their wild relatives, and they can also reveal the remarkable range of variation that could only belong to a long-domesticated animal.

The photo below (direction of travel toward the top) illustrates a number of core features that are shared by dogs, foxes, coyotes and wolves. The front track (lower left) is larger than the rear track (upper right). Both front and rear tracks have four toe impressions, and a single smooth middle pad. The tracks are symmetrical, meaning that if an individual track were divided down the middle and the right half were folded over onto the left half the two halves would superimpose almost perfectly.

There are a few additional traits in these prints that are shared among some–but not all–dogs and their wild relatives: The overall outlines of both front and rear prints are oval, the toes are held tightly together, and the claw marks point straight ahead. The larger ridges between the toes and the middle pad form the celebrated canine X, and the center of each track is occupied by a rounded dome or plateau. But although the tracks are roughly coyote sized, we see several additional traits that indicate dog rather than coyote. The claw marks are wide and deep, the middle pad of the front print is large compared to overall size of the track, and its trailing edge is rounded.

A comparison between the dog tracks above and the coyote tracks in the next photo will highlight the differences. (The coyote front print is below and a little ahead of the rear, and the direction of travel is to the right.) Like the dog tracks, the coyote prints are compact, with oval or egg-shaped outlines and tightly held toes. But some of the claw marks are missing, and those that are visible are delicate rather than robust. The middle pad of the front track is relatively small, and its trailing edge is concave.

The dog front track shown in the next photo is even more of a departure from the two preceding illustrations. Instead of being oval the print is round in outline, and the toes, especially the inner and outer ones, are widely spread and angled to the sides. The upper arms of the canine X seem to have been pressed apart, and there’s a curved ridge instead of a dome at the center of the track. Like the previous dog tracks, the print in the photo below has wide claw marks and a large middle pad. A track like this is easily recognizable as dog.

The photo below shows another dog track variant. The overall outline is rounded–in fact the print is a little wider than it is long. In contrast to the triangular middle pads of the previous dog tracks, this print has a trapezoidal middle pad with a broad leading edge. Instead of an X the internal ridges form a distorted H shape, and there’s a horizontal ridge rather than a dome in the center of the track. The absence of claw marks is unusual for a dog print. This is the kind of track that might be mistaken for a feline–a house cat, bobcat, or even a cougar depending on the size of the print. But there are clues that indicate dog, and they become obvious if we look at a true feline print.

The photo below shows the right front track of a bobcat. If we test for symmetry using the folding test described in the second paragraph, we can see that the dog track above is symmetrical and the bobcat track below is asymmetrical. There’s a leading toe (second from left) and a trailing toe (rightmost) in the bobcat print, and the middle pad is canted to the right. Instead of the canine X we see an angular C-shaped ridge that is also canted to the right. Another important feline trait is the contrast in size between the large middle pad and the small toes.

Wild canines have a way of placing their feet quietly, without tension or unnecessary movement. Dogs, on the other had, often express slight jiggles or shifts in the movements of their legs, and the difference can sometimes be seen in their tracks. In the photo below you see two dog tracks (in the upper left, the front a little below and behind the rear) and two coyote tracks (the front in the upper right corner and the rear just below the two dog tracks). Displaced bits of snow lie inside and around the edges of the dog tracks, while the coyote tracks have mostly smooth floors and margins. The best way to see the action that produces this kind of difference is to watch a dog walking or trotting directly away from you. You may see subtle shifts in the body or slight wobbles as the legs contact the ground.

Dogs lead easy lives compared to wild animals, and this often shows in the trails they make. The tracks of three creatures can be seen in the photo below. A dog meandered from top left to bottom right, leaving two partly superimposed tracks in the upper left corner, two tracks close together midway down the left side, and two more widely separated tracks at the lower right. A coyote trotted from top to bottom leaving smaller direct register prints, one between the dog tracks in the upper left and another at the lower left. And my boot tracks can be seen to the right of the dog tracks.

Wild creatures cannot afford to waste energy. There are exceptions: young animals play, and during mating season mature animals can make some wacky moves. But the business of survival demands efficiency of movement. Dogs, on the other hand, can expend energy without the pressure of finding their next meal. The coyote in the photo above had a destination in mind and moved with purpose. The dog was well fed and carefree, and counted on finding food and shelter when it got home. And I was focused on the story those tracks told about the lives of dogs and and their wild relatives.

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.

Animal Artists

Nature is the original artist. Whether it’s the pattern of ice crystals in a frozen stream or a flock of birds wheeling together in the sky, we’re surrounded by striking compositions. And animal tracks are no exception. I’ve been photographing these works of art over the years, and I’d like to share some of my finds with you. For each one I’ll also include my deductions and speculations on how it came to be.

Those are mouse trails (deer mouse or white-footed mouse) that seem to pour out of the upper right corner of the photo below. In each trail the deeper landing spots are connected by lighter tail marks. The indistinct trail farthest to the right is older than most of the others. To the left of that one is a trail (superimposed on another older one) that looks like it is heading uphill, based on the shorter jumps and the angles of the tracks. The next one to the left (mostly centered in the photo) seems to be a single passage, and a few tail marks that go to the side (check out the small mark above the lowermost landing spot) tell me that the mouse was going downhill. The trails farther to the left are combinations of at least two passages, and it’s hard to say which way the animals were going. All of the trails radiate from a depression in the snow next to a tree trunk at the upper right of the photo. Openings like this allow access to spaces under the snow pack which are crucial for the winter survival of small animals.

The tracks pictured below were made in a warmer season. A toad walked through the mud and left some natural calligraphy. The direction of travel is from right to left, and the front tracks, with their four toes oriented inward, lie inside the rear ones. The curved lines were made as the trailing toes of the front feet occasionally dragged through the mud as they touched down. Toads often seem to walk on the tips of their rear toes, which is why the hind tracks look like curved rows of dots. The difference between the front and hind prints is best seen in the tracks from the left side (the lower ones) where there’s more separation between the two. At the extreme left there are two left rear tracks near one left front. It looks like the toad put its rear foot down lightly, picked it up and put it down more firmly nearer to the front print.

If you’re having trouble picturing how the feet of a toad could be positioned to make tracks like these, this photo of an American toad might help.

Snakes can also produce artistic creations. A garter snake made the designs in the sand shown below. The sinuous trail near the stones was made by simple forward movement toward the upper left. You can see several places where the tail must have lifted and the back end moved slightly sideways, leaving a ridge outside of the main groove. It’s harder to figure out what happened in the lower half of the photo. The wider flattened areas suggest sideways movement, almost as if the snake was having a good stretch. Do snakes do that?

Meadow voles bulldozing their way through shallow snow made the next work of art. You can see tiny tracks in the grooves, too many to have been made by just one passage. Tail marks show in a few places. The haphazard nature of the voles’ travel suggests they were searching for something edible, seeds perhaps.

A crow is the featured artist in the next photo. The bird landed at the lower center and walked toward the deep hole just above center. It must have dug around there, maybe in search of some edible item. (Or did it already have something that it put down and manipulated there?) It then turned to the right and took off, leaving a tail mark to the left of the hole and a pair of nearly symmetrical wing marks to the right. (If it had been landing instead, the wing marks would be next to or to the left of the hole.) There are some additional feather marks in the photo that are harder to figure out. The ones in the lower right corner that seem to drag down to the left may have been made when the crow landed. Just above those there’s another set of wing marks, and there are two more on the left side of the frame, one above and another below the tail mark. These are more of a puzzle, since they don’t seem to be connected with the landing or the take-off. Maybe the crow swooped around before it actually landed, or maybe another crow was harassing it.

I’ve saved my favorite one, a red fox track decorated with ice crystals, for the very last. This is an interesting phenomenon that occurs during very cold weather. When the track was made it would have looked normal, with a thin floor of compressed snow bordered by low walls of snow. After the fox stepped there the temperature stayed cold so the soil beneath the track, although frozen, was warmer than the air above. The warmth at ground level caused ice in the ground and the snow in the floor of the track to undergo sublimation and recrystallization. Water molecules became detached and formed water vapor, which moved upward and formed new ice crystals in the colder air just above. Since this was a slow process the new crystals had time to get much larger than the crystals in the original snow.

This same process gradually transforms solid snow at the bottom of a deep snow pack into a warren of tunnels and chambers. Remember the mouse trails in the first photo? The trails connected to an opening which gave the mice access to spaces under the snow pack created in the same way as the crystals in the fox track, by sublimation and recrystallization. You can read more about this process, called constructive metamorphosis, here.

Natural art is all around us, and expressed within this beauty are the lives and relationships of living things and the physical world they live in. It’s certainly possible to appreciate the art of nature on its own, without any deeper analysis. And if that is your inclination I encourage you to simply be open and drink in natural beauty whenever you can. But for me, understanding how nature works adds much more to my experiences of natural art. For instance, when I look at a track filled with ice crystals I both marvel at the delicate design and imagine how that design was created by water molecules drifting up from below and attaching to crystals at higher levels. I revel in both the beauty and the finely tuned interactions that produce it.

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.

Getting to Know Porcupines

I’ve been thinking about porcupines. There are porcupines in central New York where I live, but they’re not common, so in that region (unlike in the Adirondacks) I don’t often encounter their tracks. But this spring we had some late April snowfalls, and on two different occasions I was surprised and excited to find porcupine trails. In the photo below (direction of travel from right to left) you can see the left front and left rear tracks. The hind track (on the left) shows the flattened sole area of the foot nicely, with the marks of the claws to its left. The smaller front print lies to the right but isn’t as clear because the thin snow fractured in the sole area and three of the four claw marks were covered by the hind print.

Those meager April snowfalls weren’t ideal for recording clear tracks, so I’m including a more revealing photo of porcupine tracks that I took a few years ago in the Adirondacks. There was a light skiff of snow on a dark, icy base, and the soles and claws can be seen clearly. Again, the tracks are left front and hind, and the direction of travel is toward the upper left. In the rear print (on the right) the sole is larger but the claws are shorter than in the front print (on the left). If you look carefully at the front track you can see the faint imprints of the front toes (which usually don’t show up at all) just behind the dark holes made by the claws. And those streaks that run toward the upper left from the front claw impressions are drag marks made by the claws as they came forward when the foot was lifted.

So what if there’s no snow? Following trails may not be an option, but porcupines leave plenty of other evidence of their presence. Their winter diet includes the inner bark of trees, both conifers and hardwoods, and the buds and leaves of conifers. Scenes like the one pictured below (on yellow birch) show how efficient a porcupine can be at removing the cambium tissues of living trees. And this kind of evidence lasts long after the actual feeding was done. Small debarked patches high in hardwoods (but not conifers) could also be due to squirrels, which may turn to bark feeding when other food is scarce. However, the amount of exposed wood in the photo below is more than a squirrel would be able to achieve.

To get at tree buds or leaves a porcupine climbs high into a tree (where the most vigorous branches are), bites off twigs, eats the buds or leaves, and then drops the twigs. The photo below shows a scattering of nip twigs which accumulated on the ground as a porky fed in the hemlock tree above. When porcupines feed on the swelling buds of sugar maples in early spring, or on acorns in late summer, they harvest and discard the twigs in a similar manner.

But twigs and branches can fall with no help from porcupines, so how do we know whether a porky was the culprit? The first clue is the relatively even sizes of nip twigs (mostly 1 1/2 to 2 1/2 feet), compared with the wide range of sizes when wind or ice damage is the cause. Another clue is the appearance of the separation site. Randomly broken branches and twigs have ragged, irregular ends. The photo below shows the clean, angled cut found on a red oak twig that was nipped by a porcupine.

To get to feeding spots high in the canopy a porcupine must climb trees, and on trees with light bark, like the aspen in the photo below, climbing marks are very visible. Aspens are sought out by porcupines in spring when the leaves are young and easily digested, and preferred trees are often visited several years in succession. Bears also climb trees to feast on young leaves, nuts, and fruits, but the spacing between porcupine claw marks, between 1/4 and 3/4 of an inch, is much closer than the spacing in climbing marks left by bears.

Porcupine dens are another unmistakable sign. Unlike many other animals, porcupines defecate in their sleeping areas, and when scat piles up they simply plow through it or push it out of the way. The trunk of the sugar maple in the photo below had a hollow space which served as a porcupine den, and the waterfall of scat which fell down from it is evidence of an extended period of occupancy. Porcupine scats are cylindrical to kidney-shaped, and they can also be found among the nip twigs dropped from favored feeding trees.

In spite of their prickly defense, porcupines are preyed upon by most medium-sized carnivores. I found the coyote scat in the next photo last winter, earlier but in the same general area where I found the nip twigs and the tracks in the April snow. The coyote could have been responsible for the porky’s death, but it’s also possible that the initial killer was a fisher, and that the coyote scavenged the carcass later. The quantity of quill fragments is surprising and makes me wonder whether any quills entered the coyote’s body.

By now porcupines have left the mature forests and moved to more mixed habitats where they can find the growing herbaceous shoots and leaves, cattails and other wetland plants, roots, tubers, and fruits that make up their spring and summer diet. There are lots of other animals which consume the same plants, so unless you actually see a porcupine having a meal it’s hard to recognize the signs of summer feeding. But if you’re alert you may find long-lasting evidence of their cold weather activities.

Logs

Living creatures see the world in terms of significant objects. We humans are no exception–for us significant features would be such things as chairs, doorways, computers, streets, buildings, picnic tables, traffic lights….you get the idea. For wild animals rocks, thickets, streams, cliffs, and trees come to mind. And then there are logs–items that we usually ignore unless we’re looking for a place to sit. Downed logs are important to many animals in many different ways, and the evidence is often plain to see.

A chipmunk sat on the log in the photo above to eat a red oak acorn. In order to get at the edible meat, the animal tore narrow strips and small chunks from the outer covering. Logs serve as feeding platforms for many small rodents, including red and gray squirrels, and the leftovers often reveal who the diner was. When squirrels feed on red oak acorns, the shell fragments left behind tend to be larger than those discarded by chipmunks.

The log above was used by a red squirrel feeding on red pine cones. As the squirrel fed it dropped the cone scales and cores on the ground in front of the log to create a large midden. Red pines are self-pruning trees and don’t offer many branch perches, so although red squirrels prefer the safety of branch perches, they sometimes need to use more earth-bound objects. Logs, stumps, and rocks can offer a good view of the surroundings and allow the animal to detect danger.

And how do we know it was a red squirrel? Although gray squirrels do sometimes eat conifer seeds, they don’t store them the way red squirrels do, and they never feed on enough conifer cones to create middens the size of the one in the photo.

Tracks on logs tell us that they can also serve as travel routes. Of course we need snow to see this kind of evidence–the light snowfalls of early winter and early spring often show the prints of animals that walked on logs. The coyote that made the tracks in the photo above found the log to be a convenient route through an area obstructed by branches and undergrowth. Walking on logs may also be quieter since leaves and debris can be noisy, even under a layer of snow. Another advantage of walking on logs is a better view. The greater elevation helps prey animals to detect danger, and predators to detect prey. I’ve found many different tracks on logs–the list includes squirrels, white-footed mice, chipmunks, raccoons, bobcats, bears, red and gray foxes, coyotes, fishers, minks, and weasels.

Logs offer these same advantages when there’s no snow, so we can be sure that animals also walk on logs in warmer weather. Without snow their tracks are difficult to detect, but we may still find evidence of their passing. A long-tailed weasel left the scat shown in the photo above on a mossy log. The scat was not quite 1/4 inch in diameter and contained hairs from a small mammal.

The logs in the photo at the head of this article are ones I visit regularly, and they often accumulate the scat of several different kinds of animals. This suggests that they have some special importance, but I’m not sure exactly why. The log in the foreground bridges a low, rocky gully, but the more distant one lies on more level ground. Both logs are large, but there are other logs nearby that are as big or bigger and don’t accumulate scat. Whatever the reason, we can be sure that each species that travels those logs takes note of the messages left by other creatures.

In addition to serving as perches, travel routes, and bulletin boards, logs may be a source of food. This log was torn open by a black bear in search of the grubs that were living and feeding in the rotting wood. Bears are not the only creatures that find food in logs–skunks, raccoons, and woodpeckers also open logs in search of edible morsels. But the size of the fragments and the distance to which they were thrown could only have be the work of an animal as powerful as a bear.

Have you heard a grouse drumming this spring? At this time of year ruffed grouse are looking for mates. The males seek out large logs, and once they find a log that offers a stable and well elevated surface they send out a kind of drumming sound with their wings. The low sound travels long distances, and the elevation of the log gives it even more range. Females are drawn to the sound, and if they’re impressed they will mate with the male. In the photo above I’m perched on a grouse drumming log, taking a photo with my old SLR camera. In front of me on the log you can see several grouse scats.

Whether they’re dinner tables, highways, message boards, pantries, stages, or even just obstacles, logs are significant objects for inhabitants of the natural environment. The evidence they present can reveal unseen dramas in the lives of animals. So before you sit on that log, take a look at it. You might be rewarded with a message that opens a window into the life of a wild creature.