Linda J. Spielman

What Goes In Comes Out

A big part of understanding animal lives is knowing what they eat. There’s lots of general information available in books and other publications, but to understand the dietary habits of the animals in one’s own landscape requires a few steps beyond that. We can observe animals when they’re hunting or feeding, and we can interpret chews, feeding sites, and feeding leftovers. But for many mammals, especially omnivores and carnivores, scat is the best tool. Scat contains the undigestible parts of everything an animal ingests, and it remains long after the creature has left the scene.

For herbivores, plant fibers make up the bulk of eliminations, so their scat has a grainy texture like the rabbit scat shown below. When herbivores eat foods high in water content their scat may be darker and softer, but the fibrous essence can still be seen.

Raccoons are omnivores, and their latrines often contain scats with a variety of contents. In the next photo you see raccoon scats with grape seeds and skins, apple seeds, ant parts, deer hairs, and the amorphous remains of deer flesh. An important safety note: raccoon scat may contain the eggs of a parasite that can infect humans, so it should never be touched with bare hands. To be on the safe side, it’s best to use sticks or other tools to manipulate scat, no matter whose it is.

The photo below shows river otter scat filled with crayfish shell fragments. In locations where fish are the main prey item, fish scales and bones will be the most common contents. In coastal marshes scats with crab shell fragments may predominate, indicating that crabs make up the bulk of the animals’ diet.

For many omnivores and carnivores scat contents vary with the changing seasons. The bear scat shown below was photographed in early May, and it’s made up of the remains of the newly emerging leaves and shoots the bear had been eating. Bears lose weight during hibernation and for many weeks afterwards because the grasses, sedges, and young shoots they must subsist on are energy-poor foods.

It’s only when higher quality edibles become abundant that bears begin to put on the pounds. The bear that left the scat shown in the next illustration had been feasting on black cherries. The summer diet of fruits and berries is often supplemented with insects, and you may find bear scats containing ant or yellowjacket parts.

Scats like that pictured below, full of fragments of acorns and hickory nuts, begin to show up in late summer. The seasonal abundance of acorns, nuts, and fruits, as well as increasing insect populations, provides a crucial, energy dense diet. At this time bears transition into a period of hyperphagia, and spend most of their waking hours seeking food or eating. The fat stores they put on will carry them through their winter hibernation.

The scat of canids reveals that their diets also follow seasonal cycles. Winter and early spring fare is mostly made up of animal prey and carrion. Signs of feeding on deer carcasses start to show up during the fall hunting season and continue through the winter. The coyote scat in the photo below contains deer hair and leg bone fragments. Foxes also feed on deer carcasses, but they aren’t powerful enough to crack large bones to get at the marrow the way coyotes do. Deer killed by hunters (and the carcasses resulting from the vehicle collisions that seem to spike during hunting season) may be preserved well enough in the cold to last through most of the winter. Carcasses of winter-killed deer also provide scavenging opportunities.

The red fox scat shown below (photographed in mid-March) contains the remains of a small rodent that was swallowed whole. There’s a leg bone in the chunk at the lower left, a molar in the piece at the top, and an incisor in the segment at the lower right. The bones are embedded in twisted masses of short hairs. Positioning its scat on the manhole cover was the fox’s way of signaling its presence to other foxes in the area. Small rodents and other small mammals are a winter mainstay for foxes and coyotes.

Like bears, canines graduate to summer foods as they become available. A sure sign that berries are in season are finds like the coyote scat shown below, filled with raspberry seeds. Note that the segments are tubular and blunt-ended rather than tapered like scats made up of animal remains.

As summer progresses, the menu widens. The red fox scat in the next photo (found in early September) contains acorn shells, apple skins, and fragments of field corn kernels.

Some scats lead to surprising discoveries. The next photo shows some gray fox scat containing the remains of a frog. Hollow leg bones are clearly visible, and when I pulled it apart I saw the still articulated bones of a rear foot. It’s a bit unusual to find frog remains in fox scat, but the really surprising thing is that I found this in early December. The weather had been mild, and apparently some frogs had not yet gone underground for the winter.

Food is central to survival, and scat can provide direct information about what animals eat and when they eat it. The many stories scat has to tell can illuminate not just feeding habits, but also interactions among animals, and interactions with the surrounding landscape. Each story adds to our connection with the animals around us.

Muskrats: Life in Two Worlds

Water and land: they pose very different challenges to the creatures that inhabit them. And yet some animals manage to live in both worlds. The muskrat is a semi-aquatic mammal, at home in the water and comfortable (although not as nimble) on land. The dome-shaped lodges made by muskrats (seen in the photo below) resemble beaver houses, but are smaller and are made with non-woody plants instead of the woody material used by beavers. When conditions are suitable muskrats make bank burrows with underwater entrances. Unlike beavers, they don’t build dams, and they prefer quiet or slowly moving water. Aquatic and semi-aquatic plants make up the largest part of a muskrat’s diet, but the animals also spend time on land harvesting non-woody terrestrial plants. They are also known to consume aquatic animals, including clams, mussels, crayfish, frogs, and fish.

A common sign of a resident muskrat is scat, usually found in small collections on rocks and logs that protrude above the water. These deposits announce a animal’s territorial claim to the pond, marsh, or stream where they’re found. The latrine shown in the next photo is on a large rock at the edge of a river, and it’s unusually large. The quantity and the combination of fresh and weathered scat indicate that a muskrat was actively patrolling its stretch of river.

On land muskrats generally move at a walk. In the next image the direction of travel is from left to right, and because of the snow the animal to placed its hind feet directly in the holes made by the front feet on the same side. A tail mark undulates between the tracks.

When the footing is more favorable muskrats use an overstep or indirect register walk. The trail in the next photo goes from upper right to lower left. Pairs of prints form an overall zig-zag pattern, and in each pair the rear track lies ahead of the front. The sequence, starting from the upper right, is right front, right rear, left front, left rear, right front, right rear. If you’ve noticed that the front prints seem smaller than the rear prints, you’re absolutely correct.

The difference in size is easy to see in the next photo. The right front track is on the left, and the right rear is on the right (direction of travel left to right). You can see all five toes in the front print–the tiny innermost toe is a little nub on the upper edge of the print just behind the full-size toe ahead of it. The four large toes of the front track are connected to the middle pad, and behind that there are two bumps that make up the heel pad. If these characteristics remind you of small rodent tracks you’re right on target. Muskrats are indeed rodents, although they have diverged from other rodents in many of their adaptations. In the rear track five toes can be seen, although the innermost toe impression is just the tip (above the other four rear toes and to the right of the third toe on the front print). The middle pad of the rear print made a partial impression at the bases of the toes, and–as is often the case–the heel pad did not touch down at all.

If danger threatens while a muskrat is on land, it hurries toward the safety of the water at a modified bound or lope. In the photo below you see a typical muskrat bounding pattern, with the smaller front tracks ahead of the larger and more widely set rear prints (direction of travel toward the top). The muskrat’s front feet slid forward into the soft mud, so the tips of the toes lie hidden in the muck. The larger rear feet didn’t sink as far and all five toes show clearly. Except for the relative positions of the front and rear tracks, this bounding arrangement is, again, reminiscent of the bounding patterns of many small rodents.

Muskrats possess a feature that is–as far as I know–unique among semi-aquatic animals: the toes of the hind feet are equipped with fringes of stiff hairs. In the next photo you see a left rear track, oriented toward the top. (There’s also part of a left front print to the lower right of the rear print.) The toes of the rear track are slender and finger-like, and the hair fringes make shelf-like impressions around them. These hair fringes add surface area and enhance the muskrat’s swimming ability. The smaller and un-fringed front feet are more suited to grasping and handling objects.

As you explore wetlands you’re likely to see swimming mammals, and you may find it difficult to know which creature you’re observing. There are clues that can help, starting with size. The smallest are water shrews and star-nosed moles. I’ve never seen shrews or moles swimming, so I’ll just point out that their size means they probably won’t be confused for anything but each other. Of the larger mammals, the ones whose tracks and sign we’re likely to find, the smallest is the mink. Minks swim with their entire body visible above the water, from head to furred tail. Their bodies are long and slim, their ears protrude from their heads, and their tails can usually be seen gently swaying from side to side on the surface. Muskrats are heavier than minks but their chunky bodies are about the same length. They swim with their heads and bodies showing above the water. The muskrat’s hairless tail is flattened vertically and can be seen undulating from side-to-side at the surface. The ears are small and don’t protrude from the head.

Next in the size progression (going by weight) is the river otter, with a body length of two to three feet and a powerful, furred tail that tapers from a muscular base to a small tip. Otters often swim with just their heads showing above water, but they may also undulate up and down or make short, playful swerves and dives. Their ears protrude noticeably from their heads. Our largest semi-aquatic mammal is the beaver, with a body length about the same as an otter but weighing up to twice as much. Beavers swim with most of the body and the tail below the water surface, and their ears protrude from their heads.

Muskrats are one of our most common semi-aquatic mammals. You may be fortunate enough to observe one in its watery habitat, or you may instead find evidence of the its presence. Either way, take time to contemplate the muskrat’s place in the panorama of living creatures and the adaptations that make it so successful.

Deer Browse

Signs of spring are all around us, but there are still some interesting discoveries to be made about the past season. Early spring is a perfect time to learn about the winter diet of white-tailed deer. We may think that deer are basically grazers as we see them placidly feeding in fields, like cows and horses. But that would be wrong. Cows, horses–and bison, to include an example of a wild species–are strict grazers and consume grasses, forbs, and other non-woody plants year-round. Deer are browsers rather than grazers. Although they feed on the same kinds of low-growing vegetation as grazers during the growing season, in winter they switch to the twigs, buds, and bark of woody plants. The deer you see in the lead photo (not my shot, but I couldn’t find a good attribution for it) are eating the twigs of a cedar sapling.

Deer do not have upper incisors, so in order to remove a twig they clamp it between their lower incisors and their tough upper palate. A jerk of the head suffices to yank the twig off, enabling it to be macerated by the molars and then swallowed. Rough breaks like those shown on apple in the photo below indicate that deer were feeding on the small twigs.

This contrasts with the sign left by rabbits and hares, which also depend on woody browse for winter food. Rabbits have both upper and lower incisors, and they make sharp, angled cuts like the ones shown in the next photo of multiflora rose.

The browsing preferences of deer vary in different regions. Some of their favorites in the northeast are sugar maple, ash, dogwood, striped maple, northern white cedar, and hemlock. In the next photo you see a sugar maple branch that was browsed by deer. The animals are not equipped to chew on larger branches, so they limit their browsing to the small twigs and buds at the branch tips. In mature forests these only become available if trees or large branches fall, which is exactly what happened in this case.

Hungry deer will eat everything they can reach, and unrelenting feeding often leaves browse lines like the one on northern white cedar in the photo below. This doesn’t affect the overall health of the stand, but browsing can have adverse effects on the growth of smaller trees.

The ash seedlings in the next photo show the excessive lateral branching patterns that result from heavy browsing. During each growing season the young trees form new twigs and buds, but each winter the new growth is eaten by hungry deer. The stunted trees are never able to outgrow the reach of the deer and eventually die.

Deer found a hemlock sapling at the edge of a field, and you see the result in the next photo. It’s hard to see the hemlock against the background because so many of the small twigs have been eaten, but if you follow the main stem up from the bottom center of the photo you’ll see how much foliage is missing.

Overbrowsing makes a difference in the appearance of forests. In the next photo you see a woodland that has been heavily impacted by winter deer feeding. The lack of understory trees makes it easier to walk through this kind of forest, and its cleaner appearance may be more appealing. But this forest is in trouble.

In the next photo you see a much healthier woodland. The spaces between the large trees are filled with young and medium-sized saplings, and these are the ones that are ready to fill gaps when larger trees die or fall.

Without a multi-aged understory, forests have limited ability to regenerate. When large trees die, there are no young trees ready to fill in the gaps. It’s true that there are seeds in the soil that will germinate quickly once openings are formed, but the delay in regrowth may allow invasive species to get a foothold. Signs of deer browsing tell us much more than the mere presence of hungry animals. There are larger lessons to be learned, and nature is ready to share them if we are willing to pay attention.

Squirrel Marking

Some animal communication is just for the moment, gone as soon as it is created, and some is more permanent. Whether it’s a patch of earth pawed by a deer, a scat deposit carefully positioned by a fox, or a twist of grass left by an otter, messages left in physical media can convey information long after the author has left the area. Squirrels are especially adept at this type of messaging, and their medium of choice is something they are intimately acquainted with–wood. Tree trunks, branches, roots–all can serve as bulletin boards for intra-species communication. One of the best times to observe squirrel marks is early spring, after the snow is gone but before new leaves limit our view through the forest.

The photo below shows an opening into the trunk of a large red maple. Hollow trees provide critical winter shelter, and this one must have been prime real estate because the hole has been bitten around the edges by a squirrel. Gray, red, and flying squirrels (of both sexes) use their incisors to declare ownership of desirable nesting spaces. Theoretically the sizes of the gouges should tell us which species did the marking, but the hole was about thirty feet up, and it’s hard to measure tiny things like tooth marks when you’re that far away.

The creature claiming possession of the tree in the next photo is easier to determine. Gray squirrels, primarily males, make vertical marks called stripes to assert territorial claims. They seem to prefer rough-barked trees like the white oak pictured in the photo, and the stripes are generally found on large trunks between 2 and 6 feet above the ground. I’ve also seen gray squirrel stripes on red oaks, chestnut oaks, hickories, and tulip trees. After marking, a squirrel may rub its cheek on the bitten area to leave its scent. You can see from the varying degrees of weathering that this tree has been marked repeatedly over several years.

Red squirrels also have distinctive ways of creating messages, and one of the easiest to find is the branch marking associated with conifer middens. Middens are accumulations of discarded cone scales and cores found below habitual feeding perches. The photo below shows a midden at the base of a Norway spruce. Most conifers, with the exception of some pines, tend to retain lower branches for years after they have died, and these provide perfect feeding perches. The oversized cones (up to 8 inches long) produced by Norway spruces are prized by red squirrels, and the middens came become quite large.

If you examine the branches above a midden you’ll probably find bite marks like the ones shown in the next photo. The image shows a Norway spruce branch which extends horizontally about four feet up the trunk. The upper surface of the branch is adorned by numerous bite marks. You can see the midden (out of focus) on the ground below the branch.

Red squirrels also make marks at or near ground level. In the photo below you see a Norway spruce root which has crossed over and been lifted over the years by the swelling root crown of a neighboring tree. This tree was part of a plantation that dated from the 1960s, and the trees were close enough together that horizontally spreading roots often passed close to the bases of neighboring trees. This also happens in other conifers when they grow in crowded stands, and the small lateral roots have thinner bark than the trunk and the larger roots.

A closer look, shown in the next photo, shows that a red squirrel has bitten through the bark of the lateral root. The light colored gouges are recent marks and the whitish ones are older, probably made the previous year and covered with dried resin.

Norway spruce plantations were established throughout the east during the Depression and also later in the 20th century. With their large crops of oversized cones, stands of Norway spruce are preferred habitats for red squirrels and are great places to investigate red squirrel marking. Other conifers were also used for reforestation projects, and if they support resident red squirrels you’ll probably find evidence in the form of marking and middens. Both branch marking and root marking are the animals’ way of defending their underground larders of winter food.

Squirrels also use their incisors for purposes other than marking, such as debarking trees to get at the living cells of the cambium. The photo below shows a staghorn sumac that was fed on by a gray squirrel. I found this a few years ago in early March, and the color of the exposed wood indicated that it had been done not long before. Late winter and early spring can be a time of scarcity; stored food supplies may be exhausted and squirrels may be forced to turn to foods which are less nutritious or harder to access. I’ve occasionally found similar cambium feeding by squirrels on sugar maples.

Squirrels, both red and gray, also tap trees when the sap flows in spring. The animals choose vigorous trees, and bites are made in living, thin-barked branches by anchoring the upper incisors and drawing up the lower ones. This creates what Sue Morse calls a d0t-dash pattern. Two fresh bites on a sugar maple branch are shown below, and above them there’s an older bite. Interestingly, the sap is not consumed immediately, but is allowed to dry. Once the water has evaporated the squirrel returns to lick up the crystallized sugar.

When we find a mark made by a squirrel, we can infer something about the availability of food or the presence of a desirable nesting site, but for other squirrels there’s much more involved. The associated cheek rub or saliva deposit is unique to the individual and carries information about its sex, health status, and possibly other characteristics. Even though receiving these messages is beyond our abilities, I enjoy finding squirrel marks and imagining the messages they convey to their neighbors.

Gray Fox Affairs

It’s been a strange winter. In my neck of the woods we had some significant snow early in the season, but no big storms since then. Temperatures have been up and down (more up than down), and with all the melting, the snow we do have has consolidated into a dense, icy layer. Much of the time the conditions have been terrible for tracking, but every once in a while something wonderful has happened: warmth and liquid precipitation have been followed by dropping temperatures and a change from rain to snow. When this happens, snow that falls while the air is still relatively warm becomes bonded to the crust. As the temperature drops and additional snow falls, it forms a soft layer on top. The result is a non-slip and easily navigable surface that is a perfect medium for recording tracks.

A few days ago I encountered just such conditions: an icy base covered by a thin layer of soft snow. I was in an extensive natural area, and both the forest road I was following and the surrounding landscape offered beautiful tracking conditions. Animals of all sorts had been moving easily over the snow, and there were tracks everywhere. I found myself following the trail of a gray fox. The animal went for quite a distance at an easy trot, but then it did something that was quite puzzling.

The photo below shows the fox trail as it goes from upper left to lower right. (You can also see a coyote trail to the right of the fox trail, and a mountain bike trail to the right of that.) As it entered the frame the fox was walking (the first three tracks at the upper left). In the next section (between the last walking step and the edge of the tree shadow) the pattern was very different, and following that the trail looks unlike either of the previous sections. I wanted to know what was going on and why the middle section looked so different.

In a situation like this the first thing to do is identify each track. The zig-zag of the walking section helps us to tell right and left, and the fact that the front foot is larger than the hind foot distinguishes front from rear. The next photo shows a gray fox front print on the left and a gray fox rear print on the right. You can see the difference in overall size and also the difference in the sizes of the middle pads.

The photo below shows just the puzzling middle section, and if you compare photos you’ll see that the front and rear in the photo above are actually the first two tracks in the middle section. It’s pretty clear that the first four prints in the photo below are left front, left rear, right front, right rear. After that it gets harder. The track just above the right rear is smaller than the one to its right, so those two prints must be left hind, left front. Three tracks from the right side come next, and it looks to me like the sequence is right rear, right front, right rear. The final two before the tree shadow are the left front and the left rear, and at the edge of the tree shadow there’s a right front with a right rear partially superimposed on it.

In the next photo I’ve added labels showing my take on right/left and front/rear. If we start at the beginning of the whole sequence, the animal was trotting (those tracks aren’t seen in the photos) and then slowed down to a walk (the first three tracks in the distance shot). The next section shows that the fox slowed even more to an overstep walk (the first four prints in the photo below), then slowed even more to an understep walk. There’s an extra right hind that’s puzzling, but I’m guessing the fox just repositioned its right hind foot. Then the overstep walk reappears after which the fox picked up the trot (the two impressions at the lower right in the first photo). Notice that the step lengths in the overstep part are shorter than the regular walk steps that preceeded them, and the step lengths in the understep part are shorter yet.

That analysis was rather involved, but it leads to a picture of what the fox actually did. As it trotted along something it detected made it slow down, first to a walk and then almost but not quite to a standstill. It was probably sniffing and listening intently as it moved very slowly. Once the animal concluded that it was okay to move on, it resumed its journey at a trot. It’s impossible, without more evidence, to know what caused the fox to react the way it did. It may have been a threat, but it could also have been something that interested it for a different reason. It is, after all, mating season for wild canines.

And the fox I was following was definitely tuned in to mating season. Farther on I found a spot (shown in the next photo) where the animal had detoured to urinate on a small spruce branch. If you look in the center of the frame you’ll see a squiggle of urine that runs horizontally from the upper edge of the spruce branch. Because the urine wasn’t squirted out the side of the tracks we know this was a female. She would have lifter one hind leg forward and supported herself on the other hind leg (plus two front legs) as she urinated. The relative depths of the tracks tell us that the supporting rear foot was the left. Its track is in the prominent double impression above and to the left of the urine.

I’ll never know what made the gray fox slow down and leave the pattern discussed in the beginning of this article. It could have been a threat–there was certainly a coyote in the neighborhood, or it could have been the mountain biker. A fisher (whose tracks I also found on that day) would have made the gray fox nervous. And there were red fox trails as well. But the trail shown in the photos above doesn’t suggest alarm so much as cautious interest. The fox didn’t change direction but just continued on. Was it another gray fox, one she was familiar with, or one she had mated with in a previous year? We have a small part of the whole story, and we can only speculate about the rest, but it’s fascinating just as it is.

Mouse Maneuvers

The mouse–not most people’s favorite creature, to put it mildly. Certainly the house mouse can be a serious pest, but wild mice are different creatures altogether. To start with, they are more attractive than the drab house mouse, as you can see from the portrait of a white-footed mouse which heads this post. The white-footed mouse is one of two species which inhabit the northeast, the other being the deer mouse. They are closely related (both belong in the genus Peromyscus) and are so similar they can’t be distinguished from tracks or sign. Habitat may indicate which one we’re dealing with, but from the tracker’s perspective it’s not really important, since they have similar characteristics and behaviors. White-footed mice prefer deciduous and mixed forests at low and moderate elevations. The trails shown below were most likely made by deer mice, which are more common in boreal and high elevation forests.

Both deer and white-footed mice are hunted by just about every predator in our region, so they stay hidden whenever they can. In warm months they find safety within woody debris, shrubs, blowdowns, rocks, log piles, and sometimes human structures. In winter, snow usually provides ample cover. Mice are able to tunnel through snow if it’s not too dense, and deep snow actually contributes to their survival. Within a deep snowpack the temperature is highest at ground level and decreases toward the surface. The temperature gradient causes ice crystals in the lower levels to sublimate and recrystallize at higher levels, leaving spaces where small animals can find safety and warmth. Hollows at tree bases, among rock outcrops, and under downed logs and branches allow mice to move between the surface and the lower regions (the subnivean zone). That’s why the trails in the photo above radiate from the base of the tree at the upper edge of the photo.

The next photo shows a steep, snow-covered embankment at the edge of a groomed snowmobile trail. A mouse (it could have been either a white-footed or a deer mouse) bounded from the lower left across the packed snowmobile trail toward the slope. The mouse turned to the right and then went under a slight overhang where it found (or dug) a tunnel leading to safety in the deeper snow bordering the snowmobile trail.

Look under the log in the next photo and you’ll see mouse trails. Notice how the mouse trails run into (or out of–or both) the cavity at the upper left, a mouse-sized hole at the lower right, and unseen openings under the lower part of the log. As long as these openings are maintained, mice can move easily between the snow surface and the subnivean realm. The log also provides protection from aerial predators.

In soft snow mouse trails on the surface often lead to holes that connect to tunnels deeper in the snow.

Both deer and white-footed mice store nuts and seeds in cavities in logs, standing trees, and rock piles. Once winter comes any space protected by deep snow makes a good feeding area. The midden of black cherry seeds in the next photo shows where a mouse fed beneath the snowpack at the base of a tree. The neat round holes are reliable indicators of mouse feeding.

Mice use logs as travel routes, but we only see evidence of this when a light covering of snow coats the log surfaces. In the photo below you see a jumble of mouse tracks, a few of which show toes clearly enough to reveal the direction of travel. There’s a rear print at the lower left that points toward the left, and you can see a few front tracks near the upper edge of the snow with toes pointing toward the right.

There are other small mammals, voles and shrews in particular, whose trails can be confusingly similar to those of deer and white-footed mice, especially when they are bounding. But the bounds of voles and shrews are less regular and have more variable foot placement than the bounds of mice. Voles and shrews also use a greater variety of gaits than mice, including walks, trots, bounds, and lopes. Voles especially are likely to make frequent gait transitions, and often use a perplexing gait sometimes described as a shuffle. Mice can walk but it’s rare, and I’ve never seen evidence of a mouse trotting, shuffling, or loping.

Deer and white-footed mice are relatively long-legged and athletic, and they sometimes make long leaps. Voles and shrews, with their chunkier bodies and shorter legs, can’t jump nearly as far. So if you find a trail with leaps like those in the photo below, you can confidently assign it to a mouse rather than a vole or shrew. The tail marks are another clue. Mice have tails as long or longer than their body length. Both the short-tailed shrew and the woodland vole, the two species most likely to be confused with deer and white-footed mice, have very short tails and wouldn’t leave long tail marks like the ones in the photo.

The white-footed mouse trails in the next photo show the typical consistency of pattern and leap length, but the one on the left demands a second look. It begins at the bottom, a little to the right of center, goes upward for a few leaps, and then takes a hard turn to the left. After a few more leaps the trail circles back to the right and proceeds toward the top of the photo where there’s a fallen branch sticking out of the snow (just outside the frame). Each time it turned the bounding mouse flung its tail to the outside for balance, leaving conspicuous tail marks. There’s a pile of snow that was kicked toward the rear where the mouse turned left, and where the trail curves back toward the right the landing/takeoff depressions are deeper. These observations suggest extreme bursts of energy.

We’ll never know for sure, but the most likely explanation is that a threat spooked the mouse. There’s no sign of an actual attack, so the mouse evidently survived, but it must have been alarmed by something. Deer and white-footed mice, along with other small rodents, are in constant danger of predation, and we sometimes find evidence of a successful hunt (see my post for March 1, 2022). But most of the time mouse trails tell us they survived to live another day.

Possum Puzzles

The opossum is a humble animal, slow moving, shy, and generally of a placid disposition. But opossums can present surprising challenges to the tracker, not the least of which is getting a handle on the tracks themselves. To understand opossum tracks it may be helpful to see the animal’s actual feet, so let’s take a look. The photo below shows the underside of the left rear foot of an opossum–it resembles a human hand with a large, widely angled thumb and four additional, finger-like toes. If you hold up your left hand with the palm facing you, you’ll see the resemblance. Try to imagine your hands as the rear feet of the animal.

In the next photo you see the opossum’s left front foot–very different from the rear. The five toes of the front foot are somewhat finger-like and similar to each other in shape, and the middle pads are quite bulbous. Both front and rear feet are adapted for climbing but are less ideal–especially the rear feet–for moving on the ground. This, combined with the animal’s heavy body and relatively short legs, means opossums are not very agile.

Now let’s look at opossum tracks. In the photo below the right front track lies on the left and the right rear track lies behind it on the right, both tracks oriented toward the left. The spreading toe indentations of the front track radiate from a compact grouping of middle pad impressions. In the rear track the thumb points to the side (downward in the photo), and the other four toes are closer together and angled to the opposite side (upward in the photo).

Because the opossum rarely moves faster than a walk (or sometimes a trot), front and rear prints are often partly superimposed, and that’s another source of confusion. (The animal whose tracks are pictured above was drinking at a puddle, so it left some nicely separated prints.) In the photo below you see a left rear and a left front track, oriented toward the right. The two tracks are so close together it’s hard to tell where one ends and the other begins. If you look at the right side of the frame you’ll see five similar toe marks radiating outward from four closely set middle pad impressions. That’s the left front track. The hollow made by the thumb of the left rear track sits just behind the front middle pads, and above it you can see the middle pad and toe indentations of the left rear track.

The indirect register walk is the opossum’s preferred gait, so we often see sequences of front and hind prints like the ones shown above. In the photo below an opossum walked from the lower left to the upper right, leaving the zig-zag pattern typical of the walk. Each angle of the zig-zag is composed of front and rear prints from one side, and in each of these couplets the hind print lies just behind the front print. The sequence of tracks is right rear, right front, left rear, left front, right rear, right front, left rear, left front.

When tracks are less distinct, possum trails can be downright perplexing. The next photo shows another walking opossum trail, again proceeding from lower left to upper right. The rear feet fell farther behind the front feet at each step, but the zig-zag pattern can still be seen. A few of the prints are recognizable as possum tracks, and the rest are just weird looking.

If an opossum needs to move a little faster it shifts into a trot, leaving a trail like the one shown in the next photo (oriented from lower left to upper right). It’s harder to sort out front and rear tracks in this trail because the snow was dry and the faster gait created more disturbance. But if you look closely you’ll see that the rear tracks are consistently just behind the front tracks. The sequence of prints is right rear, right front, left rear, left front, right rear, right front, left rear, left front.

We know it’s a trot because the trail is straighter than the walking trails shown in the previous photos, and the distances between the sets of tracks are slightly greater. There must have been a slight hitch in the gait of the animal that made this trail, because the claws of one of the right feet (it’s hard to tell whether it was the front or the hind) seemed to brush the snow each time it moved forward to the next landing spot.

You may have noticed that none of the possum trails I’ve shown so far have tail drag marks. Opossums don’t drag their tails as often as people may think, but it does sometimes occur. Here’s a photo of a possum trail (oriented from upper left to lower right) with a nice tail drag mark. Don’t worry if the direction of travel isn’t obvious–it’s hard to tell from the photo because of the angle. A fox left a galloping trail on the left side of the frame, moving from bottom to top.

Much of the opossum’s winter diet comes from scavenging on carcasses, and the animals don’t generally move very far away while a food source lasts. So if you come across a possum trail it’s worth following–you may find a feeding site, or even a den like the one shown in the next photo. I had to climb through and around lots of tangles and thickets, but I eventually found the den the opossum was using while it fed on a deer carcass not far away.

Opossum tracks and signs give us a window into the lives of the animals. But I’m fond of them for an additional reason: the tracks are just so quirky. In fact, the consistent peculiarity of possum tracks is one of the clues to their identity. So be alert for weirdness, and when you find it, consider the opossum.

Where Do The Bones Go?

Have you ever wondered what happens to all the bones? Animals are dying all the time, and when they die their soft tissues are eaten by predators and scavengers, picked off by birds, ingested by insects, and decomposed by microorganisms. This leaves just bones, like those of a rabbit shown below. But we don’t see bones littering the landscape, so what happens to them?

First let’s consider small animals. When a tiny creature such as a vole is killed by a predator, the catch is swallowed whole and the bones are crushed and partly assimilated. Undigested bone fragments are eliminated in scat (or pellets if the hunter was a hawk or owl). You can see small bone fragments in the red fox scat shown below–there’s also plant material, tiny hairs, and what appears to be a whisker. Scat like this will eventually be weathered and dispersed into the soil. Even if a small animal isn’t completely consumed immediately, its remains will be broken down, dispersed, and probably hidden from our view by its surroundings.

But what of larger animals whose carcasses would be more obvious? Deer immediately come to mind, but the question also applies to bears, coyotes, woodchucks, raccoons, and other similar sized animals. We do occasionally see the remains of recently deceased animals, like the deer carcass in the next photo, but why don’t we see piles of old bones lying around everywhere?

The answer has to do with the nutritional value of bones. The deer femur in the next photo was cracked open by a coyote to get at the marrow. (I say coyote because the only other animal in our region which is powerful enough to break a deer leg bone would be a bear, and there were no bears in the area where the bone was found.) Toward the upper end of the larger piece you can see some striations which were probably made by the coyote’s molars as it worked at the bone.

We sometimes see evidence of the utilization of bones this way in scat. The coyote scat in the next image contains an abundance of deer bone fragments and deer hair. The hair would have cushioned the sharp bone edges and prevented injury to the animal’s digestive system. It wouldn’t take long for bone fragments like these to be hidden in the upper layers of soil.

In addition to marrow, bones contain calcium, phosphorus, and other minerals which may be lacking in the diets of wild animals. Mineral deficiencies are especially likely for herbivores. Many animals supplement their nutrient intake by chewing on bones, and they usually choose less daunting ones such as scapulas, ribs, and vertebrae. The bones of birds, reptiles, and smaller mammals such as rabbits can also be utilized by less powerful animals. Even deer have been observed chewing on bones. This kind of chewing may not leave obvious signs–just ragged edges, missing ends, or random gouges.

Rodents also gnaw on bones, and the evidence of their activity is often more conspicuous. In the next photo you see a segment of deer leg bone lodged on a midden at the base of a Norway spruce tree. Middens, piles of discarded cone cores and scales, are created when a red squirrel repeatedly uses a favorite perch to feed on cones. The red squirrel that claimed this tree must have used the same perch to work on the bone.

In the next photo you can see the grooves made by a squirrel’s incisors as it chiseled off bone shavings.

Smaller rodents, like voles and white-footed mice, leave finer grooves like the ones in the next photo.

These creatures weren’t after marrow, since the bones were relatively old and the marrow had been removed long ago. This behavior is probably driven in part by the need to supplement their mineral intake, but rodents also chew on bones (and antlers as well) to maintain their teeth in good condition. Their incisors grow constantly, and are subject to malocclusion if not shaped and worn down with regular gnawing. The same is true for rabbits and hares, which are also known to gnaw on bones.

As time passes carcasses are pulled apart and bones are cleaned of soft tissue, scattered, broken, crushed, pulverized, chewed, and ingested by many different animals. Rather than piling up as useless cast-offs, animal bones gradually disappear as they are utilized by living creatures. Animals are part of the web of life both while they are alive and after they are dead.

Conspicuous Communication

If you’ve ever found a pile of feces perched in a conspicuous spot, you’ve encountered a message from an animal. Canines are especially likely to communicate this way, and they’ll use any location that makes a good exhibit. The photo below shows red fox scat displayed on the base of a fallen log. There’s both recent and older scat–recognizable by its lighter color–indicating that this location has been used more than once. One older chunk is nestled in the center of the new deposit and another rests below it on a shelf of wood.

Our olfactory abilities are too limited to appreciate the complex bouquet of chemicals in scat, but for canines–and probably other species–each deposit conveys information. The specific content of the communication could be establishment of a territorial boundary, advertisement of mating availability, or reinforcement of group cohesion. Scat can also indicate the health, status, and identity of the animal which produced it. The coyote scat in the next photo was in the center of a road rather than on a raised object, but it’s placement made it noticeable nevertheless. I found this in June, when we would expect coyote parents to be leading their offspring on short explorations, and my best guess is that the message was territorial in nature.

Important locations may accumulate a number of deposits. The rock in the next image must have been significant, because there are four different scats on the rock and several more which fell off to one side and aren’t visible in the photo. All of the deposits were left by red or gray foxes, and the contents include apple skins and seeds, hair and small bones, and insect parts. The most intriguing one is the chunk at the lower right.

A closer look shows that it contains porcupine quills.

An ant mound formed the pedestal for the red fox scat in the next shot. I found it in early spring, so the ants would still have been deep underground when the animal stood on the mound and dropped its feces directly on top.

Manhole covers can provide suitable display locations. The red fox that left the scat in the next photo had dined on a small rodent, as indicated by the short hairs and small bones it contained. The manhole cover was in a grassy trail and allowed the scat to stand out in the uniformly green surroundings.

Sometimes scat seems to represent an assertion of confidence. Coyotes will kill foxes, so the smaller canines are usually careful to avoid encounters. In the photo below a recent gray fox scat (at the lower right) sits on an older accumulation of coyote scat. The deer hair in the coyote scat shows that the animal had scavenged on a mostly cleaned out carcass, while the gray fox had eaten meat from a fresher carcass.

Any protruding object is a potential platform for canine scat. The photo below shows a deposit of coyote scat on a pile of horse dung.

In the next photo you see one of my most surprising finds. A gray fox had deposited scat on top of a rock cairn which marked a trail junction. This must have required a delicate balancing act, because the pile of rocks was tall enough that the fox would have needed to place at least one rear foot on the cairn.

The conspicuous locations often chosen by wild canines mean that we often notice the scat left by wild canines. We’re less adept at interpreting the messages contained therein. But even if we miss what’s most important to the animals, it’s fun to enjoy the creative and sometimes whimsical positioning of the scat of foxes and coyotes.

Seeing the Forest And the Trees: Lessons from Raccoons

Details versus the big picture–in tracking we need both, but sometimes one can get in the way of the other. We can focus too closely on the small details and miss the overall view, or we can see a larger pattern but miss the crucial fine points. The tracks of the raccoon present challenges on both levels, so they can be helpful for balancing both perspectives.

In the photo below you see two raccoon tracks, a left rear (on the left) and a right front (on the right), oriented toward the top of the frame. Both tracks have the five finger-like toes characteristic of the raccoon. Indentations made by the claws can be seen ahead of each toe, and the undivided middle pads show behind the claws. There are also heel impressions in both front and hind tracks. They’re not as deep as the impressions of the toes and middle pads, but they show up because their texture matches the texture of the other parts of the tracks.

Compare the left rear track shown above to the left rear print in the next photo. In the image below the toes are also finger-like, and they’re held even more tightly together, but the middle pad looks different–it’s shaped like a trapezoid rather than a C. There’s also no heel impression.

The next photo shows a right front print. It’s toes are similar to the toes of the right front in the first photo, but they spread less. And the middle pad is not quite the same; instead of being symmetrical it extends farther back on the outside of the foot. Another difference is the lack of a heel impression.

In general front tracks are smaller than rear tracks and have more spread in the toes. The middle pads of front and rear prints also differ: those of the rear tracks are generally broader with more gently curved front edges than those of the front tracks. Because of these differences it’s usually possible to tell front from rear prints in the raccoon.

It gets trickier when the tracks are incomplete. In the photo below of a right front raccoon track (oriented toward the left) only four toes show, and they’re not very finger-like. The middle pad impression is faint, and you need to look closely to see the curved leading edge. This kind of track could easily be mistaken for that of a different animal.

But we don’t want to miss the forest for the trees. The arrangement of a series of tracks is as important as the details in the individual tracks. The image below shows the typical pattern of a raccoon moving at a pace-walk from right to left: tracks in sets of two, each pair composed of a front from one side roughly next to a rear from the opposite side. This is different from the regular walk commonly seen in deer, house cats, dogs, and wild canines, in which the superimposed front and rear tracks from the same side form a zig-zag pattern. In the raccoon trail shown below the details of track structure that were covered in the preceding paragraphs allow us to distinguish front from rear prints. For instance, in the pair of tracks at the upper right the rear print (larger with a broader middle pad) is above and a little ahead of the front print (smaller with a narrower middle pad). The sequence of tracks, starting from the right, is left front, right rear, right front, left rear, left front, right rear. In each pair the rear print is a little ahead of the front. This position isn’t a constant–the relative placement of the two tracks in a pair can vary, but is usually maintained unless the speed or attitude of the animal changes.

With that pattern established, let’s look at an interesting variation. The photo below shows a similar pace-walk pattern, again proceeding from right to left. Although the track details aren’t as clear the relative sizes suggest that the sequence, starting from the right, is right front, left rear, left front, right rear, right front, left rear, left front, right rear. But what are those extra marks? In each of the left rear prints ( the ones in the first and third pair) there’s a deep gouge behind and some light claw drag marks ahead of the actual track. And the right rear tracks (the ones in the second and fourth pair) seem to be connected by continuous drag marks. Grooves and drag marks like these are not usually seen in raccoon trails and indicate that the animal was injured.

This close-up shows the details better.

By the way, you may have noticed a few gouges in the snow in the first pace-walk photo. These aren’t foot drag marks because they don’t connect with the tracks. The best explanation is that the raccoon was carrying something, probably a prey animal, that hung down and touched the snow at every other couplet of tracks. We see this kind of evidence more often in canines and felines, but raccoons will take small mammals if the opportunity presents itself .

Now that we’ve explored raccoon tracks at both detailed and big-picture levels, here’s a final example. When thaws or seasonal changes create seeps in the winter snowpack, raccoons are quick to explore them for edible items. In the photo below a raccoon made two trips between seeps, leaving muddy drips and beautiful mud tracks on top of the crusted snow. The upper trail goes from left to right and the lower one from right to left. In each trail the pace-walk pattern is clear, with the larger rear prints falling slightly behind the smaller front prints. The track details show nicely: the finger-like toes, the narrower middle pads of the front tracks, and the tighter arrangement of the rear toes.

The forest and the trees–both the big picture and the fine details are necessary in tracking. And it’s even more complicated, because there are more than two levels. There are details within details, and larger views beyond large views. The ability to move among many levels is not only essential for effective tracking. It adds depth and excitement to any tracking experience.