Category: scent marking

River Otters: Living in Two Worlds

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

Photo by Scott Levine, Finger Lakes Land Trust

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

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

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

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

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

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

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

Incisive Communication

Communication is an essential part of life for all animals. For squirrels and their kin spring is a time of intensive communication, as they select nest sites and prepare to birth and raise young. And the leafless canopy of early spring affords good visibility, so it’s a great time to spot the messages left by these animals.

The strong, sharp incisors possessed by all rodents–two in the upper jaw and two in the lower–are perfect tools for inscribing messages. In the photo below bright gouges show where a squirrel bit into the sides of a narrow cleft in a tree. The cleft was at eye-level, so the reddish marks of the animal’s incisors were easy to see. After making the bites the animal may have rubbed its cheeks on the bark to leave a scent message. Squirrels have a well developed sense of smell, so the saliva left in the bites and the scent from the cheek rubbing may have been even more meaningful than the visual marks.

Squirrels also create “stripes” on tree trunks. In the next photo gray squirrels–probably more than one–made many bites in an elongated zone between four and six feet off the ground along the trunk of a white oak. If you look carefully you’ll see that the individual bites vary in color, from bright reddish (the most recent) through grayish red to dull gray (the oldest). The varying age of the bites indicates that this stripe has been worked in the same way over several years. The individuals making the bites probably also did some cheek rubbing, so the bark would have been perfumed with an abundance of scents.

Marks like the ones pictured above are usually found in the general vicinity of nesting or feeding areas, but sometimes the bites seem to indicate a claim to a particular nest site. I’m not talking about summer nests, the leafy dreys seen high in the branches of large trees. In areas with cold winters, both winter and birthing nests are located in safe, weather-proof sites like hollow trees or underground cavities, and the supply of good sites may be limited. The hole shown in the photo below was located about 20 feet up in a large tree. There was probably a perfect nest cavity inside–the opening looked well used, and the varying intensity of the bitten areas suggested that the site had been used for at least several years. By marking the opening, the resident squirrel was able to establish ownership of its chosen refuge.

Squirrels are not the only creatures associated with tree holes. The openings shown below were made by pileated woodpeckers. From a distance the bright margin of a woodpecker hole may look like the chewed edges of a squirrel hole, and the size and shape may be about right. But it’s easy to tell that these holes are not squirrel holes. The first clue is their rough, splintery margins. Another clue is the number of holes–in this case there were five similar openings distributed along the trunk. These holes were made for feeding, and they’re distributed up and down the trunk because the insects the woodpecker was seeking–probably carpenter ants–had colonized much of the tree. Woodpecker holes are often more irregular in shape, and when that’s the case it’s easy to tell that they weren’t chewed on by squirrels.

Whether a mark was made by a red or a gray squirrel is often hard to determine–both are known to make stripes along trunks, and both probably mark the entries to nest cavities. Flying squirrels may mark in similar ways, but I haven’t been able to find any mention of that in the tracking literature and I don’t have any examples to share. If anyone knows the location of a definite flying squirrel nest hole, I’d love to hear about it.

Chipmunks tend to use underground refuges rather than tree cavities, and I haven’t seen anything in the literature about chipmunk marking. But a few weeks ago I came across the hole in the photo below, located a little above my head in a small tree. It puzzled me at first because the chews looked rougher and more irregular than the typical squirrel chew. But the mystery was solved when I stood on my tip toes to get a closer look. Out of the hole came the frantic chittering of a chipmunk. The animal sounded so upset that I left quickly, but I thanked it for showing me what a chipmunk can do with its teeth.

Black Bear Days

Black bears habitually cover great distances in search of food, moving from one source of edible treasure to another throughout summer and fall. The animals often find our trails and primitive roads to be convenient travel routes, and the muddy spots that develop in rainy weather are an ideal medium for capturing their tracks. I recently found these tracks on a forest trail used by snowmobiles and ATVs. The direction of travel is to the left; the left rear print is at the lower left and the left front is at the upper right. Bear tracks, especially those of the hind feet, may remind you of barefoot human tracks, but beware–the largest toe lies on the outside of a bear’s foot rather than on the inside.

But even when there’s no mud, you can learn a lot about the daily lives of bears by observing the sign they leave. Bears love fruits of all kinds. The bear that climbed the shadbush trees pictured below probably knew they wouldn’t support its weight. But no matter, it was easier to eat the berries while standing on the ground anyway.

When apples start to ripen, bears climb the trees to get to the sweet fruits in the highest branches. The gouges in the photo below show how the bear’s claws slipped downward before they caught firmly enough for the animal to move farther upward. When feeding on apples or other fruit, bears sometimes break branches and leave them hanging in the tree or on the ground below. Smaller animals like raccoons and gray foxes also climb trees in search of fruit, but their claw marks are narrower and do not show the separation distances of one inch or more that are typical of adult bears.

Insects are a much sought-after source of protein, and bears dig up nests and tear open logs and stumps to get at grubs and larvae. Even whole tree trunks are not too much for a bear’s power. The snag in the photo below was dismembered by a bear. No other animal would have been able to break out the large sections of wood and scatter the fragments in several directions.

It’s not always possible to determine exactly what a bear was after, but in the case of the tree above the evidence–the remains of carpenter ant galleries shown in the photo below–was still present in the large wood sections. Carpenter ants don’t actually eat wood. Instead they use trees as nest sites, and the tunnels and galleries they create in dead wood serve to house their eggs and larvae. Once an ant nest is exposed by a marauding bear the adult ants flee, but the eggs and larvae, and probably a fair amount of wood, are scooped up and consumed en masse.

Bears are also concerned with the movements of other bears, and they keep tabs on each other through various kinds of messages. The bites which decorate the balsam fir shown below were made by a bear standing on its hind legs. To leave such marks a bear sets an upper canine tooth in the bark and draws the lower canine in. This leaves dot-dash patterns like those to the left of the debarked area. The debarked area itself resulted from repeated biting, and the weathered appearance of the exposed wood tells us that the marking had been going on for a number of years when the photo was taken. Such marks may be visible to bears at close range, but more importantly, they hold the scent of the animal which made them, and bears are famous for their keen sense of smell.

This was a large tree, and it must have been a magnet for every passing bear. It stood about twenty feet off of a seldom-used hiking trail, and between the trail and the fir tree there was a narrow passage with distinct step spots. These step spots were created when approaching bears walked toward the tree with an exaggerated swagger, planting each foot deliberately as if they wanted to leave as much evidence of their visit as possible. In the photo below the step spots show as brown areas of bared soil.

Bear sign, and sometimes tracks, can be very abundant, but unless there’s an artificial attractant (such as garbage or handouts) they’re seldom seen. But fortunately for us their strength and resourcefulness can be observed in their tracks and sign. We can even read, albeit on an elementary level, their messages to each other.

Red Squirrel Housekeeping

The snow is gone and leaves have not yet filled in the forest canopy, so it’s a great time to look at red squirrel middens. Conifer seeds make up a large percentage of the red squirrel diet, and the animals spend lots of time eating or collecting conifer cones. To get at the seeds a squirrel holds a cone in both front feet and, starting at the bottom, chews off each scale and eats the exposed seeds, spinning the cone as it works its way toward the tip. This is done with typical red squirrel energy, and the scales seem to fly out at blistering speed. The scales and cone cores accumulate around or below the feeding station, and the resulting piles of debris, called middens, can be quite sizable. The mounds in the photo contain mostly the cores and scales of Norway spruce cones. Middens this large must have accumulated over a number of years, probably during the residence of several different animals.

The hole just below the trunk of the closer tree is an entrance to an underground space where cones were stored. These food caches are often located in the spaces around the roots under the middens, but may also be in rock cavities, log piles, or even human structures. They are generally underground where the high humidity prevents the cones from opening.

Red squirrels depend on stored conifer cones for survival over the winter. In late summer and early fall conifer stands resound with the sound of objects hitting the ground as the animals nip the cones in the tree tops. Once a good supply has fallen, the squirrels descend and carry the cones to their underground storage spaces. It’s this habit of creating concentrated supplies in a limited number of locations, called larder hoarding, that allows the animals to inhabit boreal forests with long, snowy winters. Imagine the effort that would be involved if, like gray squirrels, red squirrels had to dig down through a deep snowpack to retrieve each individual food item. With its food stored in larders a red squirrel merely needs to maintain tunnels leading from the surface to the ground-level entrances.

Middens are usually located at the bases of the trees which provided the cones, indicating that the squirrels bring cones up from storage to perches higher in the tree to feed. In the photo above you can see a Norway spruce with several branches (dead but still strong enough to support a squirrel) which could have served as feeding perches. These branches, or ones nearby, are often marked by the squirrels. One such branch is shown in the photo below. The shot was taken from directly above the branch. You can see some partly eaten spruce cones on the ground below in the upper part of the photo, and the dark tree trunk in the lower right-hand area. The branch itself is liberally marked with the fresh gouges of red squirrel incisors, and there are a few older gouges from previous years. The scent compounds left in the wood would establish the resident squirrel’s ownership of that particular real estate.

Middens tell us how much red squirrels depend on conifers for their winter food supply–and it’s not just Norway spruce. Where pines, hemlocks, firs or other spruce species are more common their cones provide the bulk of the winter diet, and similar middens can be found.


In the mixed forests of central New York, middens tell us about the non-coniferous foods that red squirrels also make use of. In the photo above butternut shells with typical red squirrel entry holes are mixed with the spruce scales and cores. I’ve also found the opened shells of walnuts, acorns, and hickory nuts in red squirrel middens. And occasionally a bone fragment, with telltale incisor gouges, sits atop a midden. Red squirrels, like other small mammals, need to boost their calcium intake by chewing on bones, and a familiar feeding perch makes a fine location for a dose of minerals.

The Allure of Scent Marking

Deep in the coldest months of winter, when you’d think every animal is single-mindedly focused on survival, some predators are being distracted by an equally compelling urge–mating. Even as the snow flies, time spent hunting decreases and behaviors connected with reproduction become more predominant. For the tracker one of the best signs of this change is an increase in scent marking. I followed a red fox trail recently, and she was detouring to urinate on raised features like this stump every 500 feet or

so. I say she because the arrangement of tracks and the placement of the urine could only have been done by a female fox. In the photo the small spots in the left half of the stump are urine (you can ignore the dark chunk of bark near the center). The fox came in from the lower left, paused on the upper side of the stump to pee, and proceeded towards the upper right. The more deeply impressed track marked SF was made by the supporting rear foot (the left) while the right rear was raised. During mating season red fox urine has a strong, slightly skunky–but not unpleasant–odor that is obvious even to us smell-challenged humans. So as I followed the trail the air was perfumed with fox musk.

My dog Banjo (dogs are great teachers for wild canine behaviors) demonstrates the technique in the photo below, supporting her weight on her right rear foot plus the two front feet and positioning her left rear leg up and forward. You can actually see the urine squirting downward under her rear end.

Male canines also raise a rear leg when they urinate, but the leg is held out and back, and the urine goes out to the side rather than downward. I don’t currently have a male dog so I can’t show you that, but I’m sure you can imagine the posture. A male coyote, traveling from left to right,

made the scent mark above, supporting its weight on the right rear foot (the track at the lower center) and shooting the urine sideways onto the upper part of the stump. Coyote urine has a mild odor and isn’t nearly as detectable by humans as fox urine is.

Bobcats also feel the mating urge in the winter, and again, those who have house cats, especially males, may have observed the technique. A male bobcat left its signature on the log in the photo below, coming in from the top of the frame, depositing its message, and leaving at the lower left.

It first gave the log a good sniff (revealed by the front print facing the log), then turned so its rear was facing the wood and sprayed urine backwards. Here’s the photo again with the tracks marked.

S denotes where the bobcat placed a front foot as it sniffed the log. RH, LH, RF and LF show the four feet in a squared posture as the cat faced away from the log and urinated backwards. Bobcat urine, like house cat urine, has a strong odor of ammonia, so if you had been there to sniff the side of the log you would have detected the cat-box odor. Female bobcats also scent mark, mostly downward from a squatting position.

Scent marking by wild canids and felids continues through pair formation, den preparation, and birthing. Soon after that hunting begins to regain its importance as the pressure to provide food for the growing young increases. But the timing of reproduction isn’t accidental. The earlier onset of predator reproduction means that their greatest need for food coincides with the greatest abundance of prey animals, which mostly mated in early spring and multiply during spring and summer.