Category: animal signs

Lean Times for Squirrels

With the coming of spring nature is breaking its winter dormancy, but we’re still a long way from the bounty of summer. In some years the food stores that carried squirrels through the winter are depleted by the time spring comes around, and when this happens the new season may bring food stress instead of abundance. This is especially true if there’s a new litter of young to raise. But over the last month or so I’ve been finding evidence that squirrels are still making use of winter’s leftovers. Digs like the one in the photo below show where an edible item was extracted. I’m confident that this was a recent dig, because the leaves around the dig were still pushed up and the soil was freshly disturbed. If this were an old dig the heavy rains we had earlier in the month would have flattened the leaves and washed the soil back into the hole.

Without further investigation it’s hard to see what the squirrel was after. When I carefully removed the leaves (as shown in the next photo), I saw not only evidence that this was a fresh disturbance but also evidence of what was removed: a firm-walled cavity that was the perfect shape of an acorn.

More proof that buried acorns are still being utilized by gray squirrels is shown in the next photo. The brightness of the acorn remnants indicates that they were not more than a few weeks old when the photo was taken in mid-April.

Instead of acorns, red squirrels rely on conifer seeds for survival over the winter, and in many locations they are still making use of the stores of cones that were gathered last summer. A few weeks ago I found a spot (shown in the next photo) where a red squirrel had extracted the seeds from a red pine cone. The bright colors of the cone core and cone scales show that the feeding activity occurred recently. Additional corroboration of recent feeding comes from weather observations. In early April we had several intense downpours, and if the cone remnants had resulted from winter feeding the heavy rain would have washed them off the log.

I’ve noticed lots of recent feeding on white pine cones this spring. In the next photo you see a midden at the base of a large white pine. The feeding perch was on the branch at the top center, and entrances to the underground storage areas can be see a little below on both sides of the feeding perch. Again, the brightness of the discarded cone scales suggests recent feeding.

A close-up of one of the tunnel entrances shows dry material that was brought out of the storage space as the resident red squirrel retrieved stored cones–more evidence of recent activity.

Even if winter leftovers are still available they may have suffered some deterioration, forcing squirrels to seek supplemental foods. A squirrel harvested the boxelder twigs shown in the next photo and fed on the buds. The end buds are missing from the twig on the left, and several lateral buds were taken off of both twigs. Why weren’t all of the buds eaten? Perhaps because there were so many buds and twigs available that the squirrel could be haphazard in its feeding.

Grubs are common in grassy areas, especially in suburban lawns, and they can be important in squirrels’ spring diet. I found the dig shown below in my back yard.

Squirrels are also known to eat conifer needles. In the next photo you see white pine needles that were fed on by a red squirrel. Compared to acorns and grubs, conifer needles don’t seem very nutritious, but they may fill a need for nutrients that are otherwise lacking.

The rising sap of deciduous trees is another source of calories, and it usually becomes available just when squirrels need an energy boost. A red squirrel tapped the black birch sapling shown in the photo below. There’s a fresh bite (with a slight greenish hue) about midway up the stem, and old bites from previous years can be seen above and below. There’s another fresh bite along the side of the stem near the top. Squirrels are expert sap harvesters and use an efficient method to extract the maximum benefit. Rather than lap up the dilute sap, the clever animals let the water evaporate and return the next day to eat the concentrated solids.

Some foods may become less available in spring, but other dietary options are simultaneously becoming more available. Squirrels are flexible in their eating habits, and this is the perfect time to observe their ability to make use of a wide range of foods.

Leafy Disturbances

Leaves: at this time of year the woody plants are bare of leaves, and last summer’s weather-beaten foliage covers the forest floor in all directions. Is there anything we can learn about the lives of animals from this seemingly mute carpet? The answer is a resounding yes! In the photo below we see a well-used deer trail. The dry, undisturbed leaves on either side contrast with the darker, disturbed texture in the trail. Even when it’s compressed, deciduous leaf litter is harder to walk on than pre-existing trails, so deer often create runs between bedding and feeding areas.

It’s not as easy to detect deer tracks if they’re not on well used trails. The next photo shows an individual deer track, orientated toward the right. The hoof pressed down into the leaf litter and the outer rims left curved depressions on the top layer of leaves. But if you just were hiking along, would this print attract your attention? Probably not. To find individual deer prints it helps to study areas where the animals have spread out from obvious trails into feeding or bedding areas.

Fall is mating season for whitetail deer, and back then the males were spending most of their time trying to attract females. Bucks made scrapes on the ground and left their scent at the site by depositing urine in the scrape. They also left their olfactory signature by rubbing their foreheads and faces on overhanging branches. The signs of these mating rituals often last into spring. In the photo below (taken a few weeks ago) you can see a scrape just below an overhanging branch still bearing a few leaves.

A close-up of the scrape has a weathered look but still shows signs of deliberate disturbance.

Deer aren’t the only animals that clear leaves. Turkeys sweep leaves aside as they search for insects and other edible tidbits beneath the leaf litter. In the photo below debris lies on top of the leaves at the bottom and lower right, showing that the turkey stood facing the upper left as it tossed the leaves backward. By using both of its feet the bird created a roughly triangular cleared patch.

But turkey feeding scrapes aren’t always triangular. In the next photo you see one that’s more irregularly shaped. There can be a lot of variation in the shape of the cleared area and the amount of displaced debris.

Buck scrapes and turkey scrapes can be quite similar, but there are ways to tell them apart. First, deer mate exclusively in the fall, so buck scrapes discovered in the spring will show signs of several months of weathering. Turkeys make feeding scrapes in all seasons, so at this time of year they range from fresh to weathered in appearance. Both of the turkey scrapes shown above are relatively recent, while the buck scrape in the preceding photos had been created about five months earlier.

Another difference between deer and turkey scrapes is their distribution. An individual buck usually makes a limited number of scrapes, almost always associated with overhanging branches, in an area he is patrolling. Turkeys usually feed in groups, and they go wherever the eating is good, so turkey scrapes are likely to be more numerous and scattered more irregularly.

Squirrels also disturb leaves. The next image shows a cleared area at the base of a tree. When I found this I wondered if it was the result of frequent use as a take-off spot by squirrels.

To check, I looked at the bark above the cleared spot (shown in the next photo) and saw that the moss and outer bark had indeed been abraded. I’m attributing this to squirrels, the most common tree climbers, but I can’t entirely eliminate the possibility that it was a raccoon. Other climbing animals are unlikely because they are less likely to climb one tree repeatedly.

Like turkeys, squirrels search for buried nuts and insects, especially in the spring when stored food supplies may have run out. Both red and gray squirrels obtain these items by digging small holes. In the next photo you see a dig made by a squirrel. Debris from the hole can be seen below and to the right, so the squirrel must have been facing the upper left as it dug.

Here’s another image of a squirrel dig, this time in a layer of pine needles. If the buried object was a nut or acorn the hole usually retains a firm impression of the object. In the digs shown in both photos the bottoms of the holes were loose and irregularly shaped, so the food items were probably insects.

Deer also dig at leaf litter in search of nuts and acorns. White oak acorns are consumed by many animals and birds, so they disappear soon after they drop. The higher levels of tannins in red oak acorns make them less palatable, so they mostly lie uneaten on the ground until soaking rains leach the tannins out. But once they’re more digestible red oak acorns are sought out by many animals, including deer. Where red oaks are the predominant oak species, areas of churned up leaves like those in the next photo (taken last December) can be found in late fall and winter. You can see fragments of acorn shells and meats the deer dropped as they chewed.

If there’s a heavy, wet snowpack in late winter that compresses the leaves, deer feeding areas may be hard to recognize by the time spring arrives. But after winters with little snow like the one we just had, the signs are evident. A few weeks ago I went back to the area where the photo above was taken to see what it looked like. In the photograph below you can see that the leaves still lie loosely in piles and windrows. There aren’t any acorn fragments to be seen–if the deer weren’t interested enough to gather them up they would have been eaten by other animals like squirrels, mice, raccoons, crows, foxes, or even fishers. You’re not likely to find fresh evidence of deer foraging for acorns because the fall crop has been mostly consumed.

Areas where the leaves were not churned up by deer (or turkeys) look very different. Fall rains and the little snow we did have were enough to flatten autumn’s leaf fall into a smooth-looking mat like the one pictured below.

Some places cleared of leaves are more mysterious . Is this the work of a deer? Or a turkey? Actually, neither.

When you see the same spot in the more distant shot shown below, you’ll see what moved the leaves: water. The close-up above comes from the area in the lower left quadrant of the distance shot below. During a heavy rain, water flowed down the trail on the right and spilled over the edge into the leaves. As the water rushed downhill it made channels in the leaves and moved them into heaps along the edges.

Leaves have stories to tell, and to understand them we need to get familiar with undisturbed leaf litter. Once we begin to pay attention to leaves, and to places that depart from the unaltered baseline, we’ll have a whole new window into the lives of animals.

Perfect Perches

Perches–they’re important to wild creatures for many different reasons. The gray squirrel in the opening image (from yardandgarage.com) is using a perch as a feeding site. The next photo shows a Norway spruce whose dead lower branches provided feeding perches for a red squirrel. You can see how the piles of inedible cone cores and scales accumulated under the branches the squirrel perched on. These accumulations are called middens, and they can build up over time into substantial mounds.

Favorite perches often show signs of usage. The red squirrel that used the perch shown below left a cone scale and a number of opened seeds, some with wings still attached.

Red squirrels may mark perches by biting them. In the next photo you see a Norway spruce branch that bears the distinctive paired incisor marks made by a red squirrel. The lower branches of conifers are usually dead, so these marks don’t heal over and may last quite a while.

In the next photo you see a discovery I made during summer a few years ago. The Norway spruce cone crop that year was early and abundant, and a red squirrel had left a cone core, stripped of its supply of edible seeds, resting on the perch it had used. And in case you’re wondering, no, I didn’t put it there, it was all the squirrel’s doing. The scales that dropped as the squirrel fed can be seen on the ground at the base of the tree.

The photo below shows an unusually well elevated feeding perch used by a gray squirrel.

In the next photo you see what I found on top of the log: the remains of an acorn the squirrel had fed on.

Here’s a perch used not for feeding but for food storage. A gray squirrel lodged a black walnut in the crotch of a honeysuckle branch. I’m not sure what the squirrel’s motivation was–perhaps it was to keep the walnut away from other squirrels.

A perch doesn’t need to be overly high to be suitable. In the next photo you see a log used by a squirrel–it could have been a red or a gray–feeding on a white pine cone.

Rocks can also make good perches. Last August a red squirrel harvested young larch cones and brought them to the rock shown below for consumption. Where rocks or logs are available they are preferred over ground level feeding sites.

But food isn’t the only thing drawing animals to perches. A red fox balanced on the log in the next photo in order to deposit its scat. Scat is important in intraspecies communication, and wild canines prefer to leave their scat in conspicuous positions. Sometimes this requires a little acrobatic ability to position the scat just right.

One of my favorite spring experiences is hearing the drumming of ruffed grouse. Males in search of mates perch on logs or other raised features and beat their wings to produce a resonant booming sound. They prefer platforms that are unobstructed and raised well off the ground. You can see a spot in the center of the image where the bark was dislodged by the drumming bird.

Perches can also be used as observation posts. In the next photo you see a mound of earth thrown up by a falling tree. There were tracks–they were barely visible so I didn’t include a photo–going up the side. The size of the impressions suggested a fox.

On top of the mound (shown in the next photo) there were obvious signs of disturbance, showing that it had been used as a perch. The fox would have sat quietly while it listened, looked, and sniffed for signs of prey animals.

We seem to have circled back around to the topic of food, so here’s my last example of a feeding perch. A black bear climbed the beech tree in the photo below and pulled a nut-bearing branch inwards until it broke off. The bear consumed the goodies, pushed the branch aside and pulled another one inward until it broke. The discarded branches formed a tangled cluster, and the bear might even have stood on the growing mass of harvested branches as it continued to pull more branches in. These branch clusters are known by the somewhat misleading term bear nests, although they have more in common with squirrel middens than with nests. With healthy beeches becoming less abundant, bear nests in beech trees are harder to find than they used to be, but the same kind of sign occurs in apple, black cherry, serviceberry, and oak trees.

Wild creatures know their territories in minute detail, and they’re familiar with all the best perches. The attributes of a perfect perch vary somewhat with the specific animal and situation, but safety and accessibility are always important. The location also needs to be appropriate to the animal’s purpose, whether it’s to consume food, to find food, or to advertise its presence. If we stay alert for perches we can begin to understand what makes a good perch and what they can tell us about the lives of the animals.

Squirrel Nests

As the leaves come down it’s easier to see into the forest canopy, and the summer nests of squirrels become more visible. The photo below shows a gray squirrel nest, a leafy structure located on a supporting branch junction. Also known as dreys, gray squirrel nests are usually located in crotches or branch junctions of deciduous trees. To build a nest in a tree, a squirrel constructs a framework of twigs and stuffs it with leaves, then makes an entrance hole and hollows out the inside of the structure. A lining of soft material such as moss or dry grass is added, and a second opening is made to serve as an emergency exit. Dreys differ from bird nests in being roughly spherical, with an enclosed interior space connected to the outside through small openings. Bird nests also lack the leafy appearance of gray squirrel nests.

Red squirrel nests are similar but are likely to incorporate a variety of materials in the outer layers. They are also more likely to be built in conifers. The next photo shows a red squirrel nest located in a larch tree. Twigs and grasses form the lower part of the nest, and fragments of plastic sheeting cover the upper part.

The nest shown above was easy to see in winter when the larch was leafless, but nests located in evergreen conifers are harder to find. The one in the photo below was tucked up against the trunk of a Norway spruce tree.

Here’s another red squirrel nest which was constructed in the crotch of a Scots pine.

There’s not nearly as much information available on flying squirrel nests, no doubt because flying squirrels are nocturnal and not as easily observed as gray and red squirrels. Mark Elbroch, in Mammal Tracks and Sign, Second Edition, reports that flying squirrel dreys are smaller than red or gray squirrel nests and are made of grasses and other fine materials rather than leaves.

In more southern climes dreys may suffice for winter lodging, but in our area squirrels move into more sheltered accommodations when the weather gets cold. Human structures are used where they are available, but hollow trees are the preferred choice for forest-dwelling squirrels. Nests enclosed in protective walls of wood and lined with insulating materials provide warmth, protection from the weather, and security. But is there any way for us to know which tree houses a nest? It’s not always possible, but there may be clues. The tree in the photo below must have had a good nesting space because it had been marked with a few bites. We recognize the bites visually, but the persistent odor of the resident squirrel’s saliva is more important to other squirrels, signaling that the space is occupied.

Red, gray, and flying squirrels all make winter nests in hollow trees. If the opening is quite small it’s probably not occupied by a gray squirrel, but beyond that, the size of the opening doesn’t tell us much about who the occupant is. I’ve found marked openings in trees where gray squirrels are absent and red squirrels are common, and also in areas where the reverse is true, so I believe that both species create bite marks to claim nest sites.

Bite marks can be sparse, like the ones above, or plentiful, like the artistic creation in the next image. I suspect that the double ring of bites was created because the owner felt threatened by the presence of other squirrels.

Nests in hollow trees continue to be useful well into spring as birthing dens. But although well protected from the elements, they have a drawback: there is usually just one entrance. In the next photo you see some nest lining that was removed from a nest and ended up in a pile on the ground. This would only have happened if a predator had raided the nest and, in the process, pulled the nest lining out. It could have been a fisher, or possibly a raccoon. Both are good climbers and fishers are considered to be specialists in squirrel predation. At any rate, nests in hollow trees are not completely safe.

In addition to clues about predation, the photo above shows us what nest lining looks like. To make this material, squirrels harvest bark and process it into finely divided strands that can be stuffed into tree cavities to provide insulation. The bark usually comes from dead branches, but may also be gathered from living stems of plants such as honeysuckle or white cedar.

The next image shows a dead striped maple branch that was stripped for nest lining. The exposed wood and fibrous remnants may bring to mind a buck rub, but buck rubs differ in several ways. Buck rubs are made on living stems that are more or less upright and have no obstructions that would hinder the approach of a large animal. Rubs are usually limited to one continuous section of the stem and occur at heights between 1 1/2 and 4 feet off the ground. Branches stripped by squirrels have random angles from vertical and could be anywhere from ground level (including fallen branches lying on the ground) to much higher. Bark is usually removed from multiple areas, and there may be a tangle of branches that would make it hard for a deer to reach the debarked sections. And finally, the wood surface of a buck rub shows signs of abrasion, while the wood exposed by squirrel stripping is mostly smooth.

Stripped branches do sometimes have telltale squirrel tooth marks like the ones in the photo below.

If you keep track of weather you’ll notice that cold nights are often followed by new bark stripping. I sometimes imagine a shivering squirrel thinking, “Wow, it was cold last night, I’m going to get more insulation for my nest!” Well, maybe it doesn’t happen exactly like that–sorry about the anthropomorphizing. But it’s clear that squirrels respond to cold with increased harvesting of fibrous bark. And it’s okay to imagine a squirrel sleeping in a cozy, insulated nest in a hollow tree on a cold winter night.

Bears: Connoisseurs of Rotten Wood

Late summer is upon us, and along with the fruits and nuts that are ripening everywhere, insects are becoming more available. Insects are an important part of the late summer diet for black bears, and the animals seek out insect populations that are abundant and easily obtained. Decaying stumps, rotting logs, and standing dead trees often harbor large numbers of grubs, ants, and other invertebrates. With their highly developed sense of smell, bears can detect these creatures even when they’re hidden deep inside rotting wood. But if they’re protected inside wood, how easy is it for a bear to get at the goodies?

Just check out the photo below, which shows a tree that was ripped apart by a bear. Large pieces of wood lie scattered around, and the inner parts are broken up and exposed. Only a bear would have been powerful enough to pull a tree apart this way. Notice how the fragments were tossed in several different directions and how some lie quite far from the base of the tree.

Logs on the ground also harbor populations of insects. The next photo shows similar signs of bear activity: large fragments tossed to considerable distances.

Stumps may hide the same kinds of food as logs and whole trees, and bears tear into them in the same way. In the next photo you see large pieces of wood that were pulled away from the stump, some tossed impressive distances. Again, this is something that only a bear could accomplish.

A bear wouldn’t exert this kind of effort if there weren’t something really good–and abundant–inside, and very often it’s the fat- and protein-rich larvae of carpenter ants or wood-boring beetles. The holes and galleries you see in the next photo (a close-up of one of the fragments from the tree in the first image) could have been made by either. It’s often difficult to know what was occupying the wood before the bear tore it apart, because everything edible has been eaten and other clues–like frass–have been washed or blown away.

Bears aren’t the only agents that cause trees and logs to come apart. We usually think of woodpecker excavations as occurring on standing trees, but it’s common for birds to open up logs on the ground. Pileated woodpeckers can do quite a job on a log, as shown in the next photo. But notice the differences: there aren’t any really large fragments, and most of the scattered pieces are quite small and close to the log.

Logs can also disintegrate without any help from animals or birds. The log in the next photo fell apart of its own accord. If you look carefully you’ll see that there’s an order to the way the pieces are arranged. The ones that were originally on the surface (one with bark and another with moss) lie at the lower left. A little above those there are chunks that were originally in the interior of the log. With a little imagination you can reassemble the fragments as they were before they fell apart, and picture the way they collapsed from the main part of the log and landed where they did.

Sometimes the goodies lie underneath rather than inside a log. The photo below shows a log section that may have sheltered an ant nest. Again, only a bear could have moved such a massive hunk of wood.

It’s surprisingly uncommon to find claw or bite marks in the wood, but recently I came across an interesting exception. The log in the photo below showed the usual signs of bear work: sizable chunks of wood tossed far from their source. But there were also unmistakable claw marks.

A close-up of the log can be seen in the next photo. What the bear was after must have been in the cavity in the center of the photo, and in the wood above it you can see claw marks. There’s a clear set of five gouges on the right and another less well defined group just to the left. The animal must have stood roughly where the camera was positioned and raked its claws downward. The wood was rather tough, but the bear was able to rip off large sections. I didn’t find holes or galleries in the wood, but there was some finely divided granular material in the cavity, which suggests an ant nest.

Bears open up trees, logs, and stumps during late summer and early fall, when insect populations are highest and grubs and larvae are fat and abundant. The foods they find in rotten wood, along with the calorie-rich fruits and nuts of late summer, allow bears to put on weight and survive winter hibernation. Every time I find a log, tree, or stump that was opened up by a bear I appreciate the animal’s strength and dexterity, and imagine how it relished the tasty (to the bear) items it found inside.

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.

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.