Category: animal signs

Canine Romance

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

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

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

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

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

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

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

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

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

Buck Rubs

Autumn is mating season for white-tail deer. The bucks sport fully formed antlers and bulked up necks and shoulders, and they’re busy sparring, posturing, and otherwise asserting their suitability as mates. Antler rubs are an important part of the bucks’ demonstrations. To make a rub a buck approaches a sapling or small tree and works its antlers up and down against the trunk. The rough surfaces at the antler bases act like rasps to remove the bark, and the tips of the tines leave rough gouges. In the center of the rub the exposed wood is bright and relatively smooth, and dislodged bark fibers may hang from the roughened margins.

Buck rubs are only made on living trees, and vertical trunks that have an unobstructed approach are preferred. Buck rubs are generally located between 1 and 3 1/2 feet off the ground and can be found on both hardwoods and conifers up to 10 inches in diameter. The light color of the exposed wood is eye-catching, but the most important part of the message is invisible. The buck deposits chemicals from scent glands in its skin by rubbing its forehead against the surface of the rub. In the process of making a rub a buck stops periodically to sniff the surface. Later, visiting does sniff the rub and take in olfactory messages that reveal the health and status of the rub maker.

Contrary to common belief, buck rubs are not connected with the removal of the velvet, the highly vascularized tissue which nourished the antlers as they grew. By late summer the rack is fully formed, and the velvet is beginning to wither and slough off. This process is assisted when the animals thrash their antlers against shrubs and small trees. By the time the rut begins in earnest the velvet is long gone.

An individual tree may be hit more than once, and a popular one may take on a whimsical appearance. Damage like that shown in the photo above may be enough to kill a young tree.

Rubs from previous years are often found among fresh rubs. Old rubs like the one in the photo below are dulled by weathering and are usually rimmed by callus formed in the growing season following the assault as the tree attempted to heal the wound.

Other animals also remove bark from woody plants, but there are usually clues that help to identify the culprit. Squirrels strip bark from stems and branches to use for nest lining, and stripped stems can look similar to buck rubs. Dead trees or branches are often the source for squirrel nest lining, and in that case we know it can’t be a buck rub. But sometimes the bark fibers are harvested from a living tree or shrub, such as the honeysuckle in the photo below. The lack of abrasion on the debarked area and the undamaged hanging strips signal squirrel rather than deer. Squirrels can gather fibrous bark from stems at any height, and the debarked areas in the photo are closer to the ground than an antler rub would be. If nearby stems or branches obstruct the stripped stem it’s also unlikely to be the work of a deer. And finally, as in the photo, stems harvested by squirrels may not be vertical while buck rubs usually are.

Debarking can also be a result of chewing. In the photo below you see a stem fed on by a cottontail rabbit. The irregular removal of bark and outer wood differs from the vertical bands left by the up and down rubbing of an antler. Rabbit feeding is also usually closer to the ground than would be expected in an antler rub, but keep in mind that deep snow can result in elevated rabbit chews. Porcupines and beavers also chew on shrubs and trees at varied heights. But like the rabbit chew, the tooth marks left by these animals are different enough from the abraded surface left by antler action to separate their chews from buck rubs.

Antler rubs are part of a suite of behaviors that allow male white-tail deer to establish dominance and demonstrate their prowess, but that’s not all there is to it. These behaviors also trigger changes in the females that prime them for mating. Sniffing a rub sends chemical signals to a doe that precipitate a flood of hormones and prepare her for reproduction. Buck rubs are part of an intricate interplay of behaviors that results, if things go well, in the appearance of offspring about 6 1/2 months later.

Beavers at Work

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

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

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

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

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

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

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

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

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

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

Checking Out Fox Dens

It’s late summer, and fox pups that started life back in late March or early April as small, helpless balls of fluff have grown into sleek coated adolescents. At about five weeks they emerged from the den, and for the next month or so they spent their time near the burrow, developing their strength and coordination through play and mock fighting. They were guarded by parents or females from the previous year’s litter, and at the first sign of danger they dashed to safety below ground. Later they began to accompany their parents on explorations and hunting forays. But even when the kits were quite mobile, the family may have continued to rely on the den as an emergency refuge. I don’t like to disturb fox families until they no longer need that safe haven, so I always wait until late summer or fall before I investigate a fox den.

Fox dens are found in settings ranging from dense cover to open, exposed areas. The den in the photo above was near a house and driveway, but it was well concealed by shrubby cover and wasn’t obvious until I got up close. In the next photo you see the other extreme–a den dug under an old pallet that was located near a highway intersection and lacked any concealing cover. Both of these are red fox dens.

A closer shot of the den in the photo above shows several entrance holes, a throw mound (at the lower right), and tracks in the loose dirt. These photos were taken during the excavation phase, and by mid-spring the den site–and the antics of the pups–were hidden by a screen of grasses and forbs.

Cemeteries are another popular spot for red fox dens. The one in the photo below was behind a grave stone and shaded by a mulberry tree. The black specks you see scattered on the dirt and grass are mulberries.

The mulberry tree was a handy source of food, and fox scat containing mulberry seeds decorated some of the grave markers.

The next photo shows a gray fox den. There wasn’t any concealing cover around the entrance, but getting to it involved a thirty-minute hike and a climb up a steep slope. Gray fox dens are usually farther from human habitation and harder to get to than red fox dens.

There are other medium-sized mammals that use burrows, and distinguishing among them can be tricky. Tracks or direct observation of the residents are the best clues, but failing that we have to rely on other features. One helpful characteristic is the size of the entrance hole: fox dens normally have openings between 6 and 12 inches across, while coyote dens can be twice that. (And like gray fox dens, coyote burrows are not generally found in places with a lot of human activity.) Woodchuck dens have entry hole sizes on the small end of the fox range and can be difficult to separate from fox dens. The most striking difference between the two is the condition of the soil around the entrance. Woodchucks use dens throughout the growing season, and the throw mound, a spreading apron of fresh dirt like the one in the photo below, shows signs of disturbance as long as the resident is active. But unlike fox dens, woodchuck dens show little disturbance of the surrounding soil. These summer lodgings may be abandoned for burrows in more sheltered areas when it’s time for hibernation, and once that happens the soil near the summer den loses its disturbed look.

Fox dens can also have throw mounds (as in the third photo), but they usually have a more trampled look due to the comings and goings of the parents. Once the kits emerge and begin playing, their antics create an area of flattened soil and plant growth much larger than the original disturbance. Active fox dens may also have scat and the bones of small animals nearby. Occasionally, as in the photo below (also in a cemetery), other kinds of toys show what the pups have been playing with.

By the time fall comes the young foxes no longer need an underground refuge, and the area around the den becomes weathered and undisturbed. Unused dens are difficult to assign to an owner and may, in fact, have different residents in the next birthing season. During the winter foxes begin to investigate den sites, and an alert tracker may notice the telltale tracks of a pair of foxes making frequent trips to certain locations. Once the snow is gone favored sites show signs of activity like those shown in the second and third photos.

Wild Turkeys

It’s a familiar sight these days: a flock of wild turkeys foraging in a distant field. Wild turkey populations have rebounded from a low point in the early twentieth century (caused by overhunting and habitat loss), and the birds have successfully reoccupied and even expanded their original range.

Turkeys spend lots of time on the ground, so we’re likely to see tracks as well as other evidence of their activities. With widths of 4 to 5 1/2 inches, turkey prints are too large to be mistaken for most other birds, and they also differ in structure from all but a few. The turkey track in the photo below has three forward-pointing toes which come together at a metatarsal pad. But unlike the tracks of birds like robins and sparrows there is no backward-pointing toe touching the ground for its whole length. Instead, turkeys may (more on the uncertainty in the next paragraph) have a spur situated higher up on the back of the leg. If you look in the lower part of the photo between the round impression of the metatarsal pad and the multicolored stone you’ll see the mark made by the spur. Because the spur indentation is angled to the right side we know that the track in the photo was made by the left foot. Canada geese differ from turkeys in having webbed feet and outer toes which curve inward. The three forward-pointing toes of the great blue heron can sometimes resemble those of the turkey, but instead of a spur the heron–like the robin–has a backward-pointing toe that usually touches the ground for its whole length and is almost as long as the other three.

Male turkeys are larger than females, so their tracks fall in the upper part of the size range. Another difference between the tracks of males and females is the development of the spur. Both sexes are born with small spur buttons on their legs, but the spurs of tom turkeys grow vigorously in the first few years of the bird’s life. In females the spur initials may develop into smaller spurs, or they may not grow at all. The size of the track in the photo–5 1/8 inches in width–plus the robustness of the spur indentation indicates that it was made by a male turkey.

In the next photo you can see two prints which measured 4 3/8 and 4 1/2 inches in width and lacked spur marks, indicating that they were made by a hen turkey. Even though there aren’t any spur marks it’s easy to tell left from right tracks, because the outer toe of a turkey is longer than the inner toe. In the track at the lower left the toe which points straight up is larger than the one which points to the right and slightly downward, so it’s a left print. At the upper right there’s a right track, with a larger outer toe (the one angled to the right) and a smaller inner toe (pointing upward and a little to the left). But beware: these differences are most clearly expressed on level, moderately firm substrates at modest speeds, and may not be as reliable under other conditions.

Spring is mating season for turkeys, so in addition to tracks you may find signs of the mating displays of the gobblers–strange undulating grooves like the ones in the next photo. These marks were made by the tips of the wing feathers as a tom turkey moved from upper right to lower left with its wings arched out and down. It left a few tracks at the lower left. And my dog added a few prints of his own to the composition.

A displaying turkey (shown in the photo below) is an amazing sight. In addition to spreading and dragging its wings, the gobbler fans out its tail, erects its body feathers, and shows off the engorged flesh on its head and neck. Several strutting toms may jostle around each other while the hens stand nearby observing and assessing. Those which pass muster will be able to mate, and in a month or so their offspring will begin to move around under the protection of their mother.

Birds are meticulous about caring for their feathers, and one way they do this is by taking sand or dust baths. Turkeys are no exception. A turkey in need of a dust bath seeks out a patch of dry soil and scrapes out a depression with its feet. It then lowers itself to the ground and rolls from side to side using its wings to throw dust over its body. At the same time the bird is fluffing its body feathers, spreading its tail, and even rubbing its head in the soil. When sufficiently coated with dust the bird rises and shakes itself off. It’s thought that dust bathing removes excess oil from the feathers and kills parasites. Good dust bathing areas are used repeatedly, leaving hollows like the one in the photo below. Feathers or scat are sometimes found around bathing sites, but the main species identifier is size. Turkey dust baths are usually more than a foot in diameter, while those of grouse or pheasants measure less than a foot.

Turkeys are one of those creatures that have returned to our northeastern forests after a long absence, and they’re well adapted to our habitats. They eat a wide range of foods, from seeds and nuts to insects and small vertebrates. They are strong fliers and powerful runners, and they are notoriously wary of potential danger. Beyond the occasional distant sightings we’re more likely to see tracks and sign than the birds themselves. But the occasional window into their lives is always a welcome find.

Sweet-Toothed Squirrels

It’s sugaring season, and the sweet bounty of spring is flowing. In sugarbushes all over the Northeast people are busy collecting the sap of sugar maples and processing it into maple syrup and other maple products. But we aren’t the only ones harvesting tree sap. Squirrels are also busy tapping trees, and the sugary nourishment makes an important addition to their spring diet.

You’ll find squirrel taps like the ones in the photo below on thin-barked branches or small trees. Black birch–pictured in the photo–and sugar maple are the most commonly tapped trees in the northeast, but they’re not the only ones. Sap containing sugars and other nutrients flows in all trees in late winter and spring when conditions are right. Sue Morse has documented squirrel taps on 23 different tree species.

To make a tap a squirrel turns its head sideways and uses its incisors to bite into the bark deep enough to penetrate the outer layers of sapwood. Sometimes, as in the photo below of a squirrel tap on a sugar maple, the resulting gouges make a dot-dash pattern. The dot is the spot where the upper incisors were anchored, and the dash is the cut made by the lower incisors as they were drawn toward the upper ones.

Both red and gray squirrels (and possibly also flying squirrels) make sap taps. Red and gray squirrels have been observed moving around in trees making numerous bites in rapid succession. But instead of licking the sap immediately they use a more efficient method, waiting until the water has evaporated and then returning to consume the crystallized maple sugar.

The squirrel tap on black birch in the next photo may have started as a simple dot-dash pattern, but it didn’t stay that way. It looks like the squirrel kept biting at it to make an irregular wound. The green surfaces are the cambium, the thin layer of living cells that produce wood and bark during the growing season. Just beneath the cambium is the wood formed in the previous summer. Its xylem cells are no longer alive, but they are connected end-to-end to form long tubes, and this is where most of the sap flow is located. Depending on the conditions, sap may also flow in the phloem cells of the most recently formed bark, located just outside the cambium. Once exposed, cambium tissue rapidly dies and turns brown, so I must have come upon this tap very soon after it was made. In the lower part of the photo you can see some dark brown bites that were made earlier in the same season.

Stems that are heavily tapped can take on a ragged appearance, as in the next photo of taps on black birch.

Once the growing season begins the tree attempts to heal the wounds. Cambium cells proliferate around the edges of the bared wood, and new callus tissue grows inwards. Small cuts may be covered in the first summer, but larger scrapes take longer. Tapping over several years can result in trees and branches covered with numerous callused scars, like those in the photo below of black birch.

So how does one find squirrel taps? Vigorous trees with plenty of exposure to the sun are preferred by the furry harvesters because they produce sap with high concentrations of sugars. Since most taps on large trees are too high for us to see from the ground, we’re limited to small trees or larger ones that have suitably low branches. But even if we find a big, healthy sugar maple with low branches it may not have any taps, because squirrels are choosey about the trees they tap. Individual trees may taste different because their chemical profiles aren’t exactly the same. Fortunately, wounds created by squirrel taps persist for months or even years, so if you locate a promising tree you may find evidence of sweet-toothed squirrels long after sugaring season is over.

Looking On The Bright Side

The leaves are down, and the colorful spectacle of autumn is behind us. The forest has gone from a kaleidoscope of color to a narrow spectrum of browns and grays. But wait, what’s that pale streak glinting among the tree trunks? If you look closely you can see it in the center of the featured photo. Moving closer we can see that it’s a buck rub, bright wood laid bare by a hormone-driven male deer. This is rutting season for whitetail deer, and the bucks are roaming the landscape seeking receptive does. They leave their calling cards on living trees–anything from very young saplings to substantial trunks 8 inches or more in diameter. To make a rub the animal lowers its head and rakes its antlers up and down against the stem. Rough areas around the bases of the antlers work like files to abrade the outer bark down to the light colored sapwood.

The photo below is a close-up of the rub in the first photo. Rubs are usually between one and four feet above the ground, and their edges are often rough or stringy. Gouges made by the short tines near the antler bases are often present–look for them just above the debarked area. The brightness of the freshly exposed wood is what attracts our attention, and it may do the same for deer. But buck rubs also carry scent messages, deposited when the animal rubs its forehead against the newly bared surface. We’re not equipped to detect these chemical signals, but to a visiting doe they convey a wealth of information about the age, health, and even individual identity of the rub maker.

The light colored areas in the photo below have also been denuded of bark, but this wood was exposed by feeding rather than by rubbing. A porcupine climbed these yellow birch trees and chewed through the outer bark to get at the cambium, the living cells that produce both bark and wood during the growing season. There’s no mistaking this example for a buck rub, but porcupine chews are sometimes found close enough to the ground to be confusing. In both cases the light wood stands out against the bark, but there are several clues that distinguish rubs from chews.

Instead of a smooth surface, wood that has been exposed by porcupine feeding is textured by tooth grooves, and the margins are more irregular, as in the photo below. The tooth marks are just deep enough to reach the nutritious tissue, and are organized with a neatness that speaks of feeding efficiency. Along the margins of chews there are often tooth marks instead of the stringy fibers that mark the edges of rubs.

Beavers, like porcupines, rely on the cambium of woody plants for much of their winter diet. Being larger than porcupines, beavers’ wider incisors give their chews a more robust appearance. And rather than climb to access food, beavers bring the food down to their level by felling trees. The beaver that felled the log in the photo below stood on its back feet to feed, anchoring its upper incisors in the bark and drawing its lower incisors upward to scrape up the cambium. It moved systematically along the log, leaving the row of shallow upper incisor digs in the bark and the longer lower incisor marks below them. Like the porcupine, the beaver penetrated just deep enough to scrape up the nutritious cambium.

Not all bark chewers show this kind of efficiency. The sumac stem below was chewed by a rabbit, and its ragged appearance contrasts with the more orderly work done by beavers and porcupines. Rabbits only feed on small stems, and their chews show varying depths of penetration with projecting splinters of bark and wood. Like beavers they are limited to what they can reach from the surface they’re standing on, but if there’s a deep snow pack or heavy snow that bends branches down, rabbit chews can be found in some surprising places.

Here’s another kind of feeding that might catch your eye in the autumn woods. Woodpeckers worked on this standing dead tree to get at the insects in the outer layers of wood. The beak strikes left pits, partially lifted slivers, and gouges (best seen on the right edge of the tree). This kind of woodpecker work can be located at any height, and may even be found on downed logs, but unlike the previous examples, it only occurs on dead trees.

Here’s a final example of eye-catching brightness. As the weather gets colder, squirrels leave their leafy tree-top dreys and make nests in hollow trees or other protected places. They gather fibrous bark for nest lining, and in the process, leave freshly debarked wood for us to find. The dead, fallen branch in the photo below was stripped of its fibrous inner bark by a squirrel. Although there’s a vague resemblance to a buck rub, the position of the branch and its non-living status indicate squirrel work rather than deer.

When squirrels harvest fiber from woody plants they may leave another clue. In the photo below you can see the paired marks of a squirrel’s incisors. Much of the bark removal is done by pulling up long strips, but occasionally the squirrel leaves a bite mark as it grasps the bark with its teeth.

Squirrel stripping is also found on living stems–I’ve seen it on honeysuckle and red cedar–and these are more likely to be mistaken for buck rubs. But areas shredded by squirrels are often in places a deer wouldn’t be able to reach, higher on a trunk, within multi-stemmed shrubs, or on stems guarded by projecting branches. Deer prefer sites with straight stems and unobstructed approaches, and any small branches or twigs are usually broken off by the vigorous action of making a rub.

I love this time of year–the leaves are down, and I can see for greater distances through the trees. Many signs of animal activity are hidden by fallen leaves, but others have become more visible. And every once in a while a bright patch shining among the duller tones draws me in and opens up a new and interesting discovery.

Bounty From Above

The season is turning, and red squirrels are obsessed with gathering food stores for the winter. They will rely primarily on the cones of spruce, fir, and pine–and to a lesser extent on larch, eastern hemlock, and white cedar–for survival over the coming months. The squirrels’ preparations for the lean times ahead leave plenty of evidence. In the photo below the ground is littered with red pine cones. A few brown cones that fell the previous year contrast with the green of this year’s crop. When stored in a humid environment the tightly closed green cones will last through the winter without opening, preserving their precious seeds until a red squirrel pulls them apart to get at the nutritious nuggets inside.

The next photo was taken in a stand of Norway spruce, a tree that is native to northern Europe but was widely used in reforestation projects in the US during the twentieth century. Some of the trees in these plantations are large and produce copious crops of cones. The cones’ large size–some as long as eight inches–means they are a bonanza of food for red squirrels.

You can see another harvest in the photo below, this time the cones of white pine. Again, it’s the largest trees, the ones that tower over the rest of the forest, that produce the best crops of cones and attract red squirrels to harvest them.

These arrays of fallen cones don’t usually last long. After working in the tree tops to drop a supply of cones the squirrel descends and transports the bounty to an underground storage space, known as a larder. A red squirrel typically has a number of larders, often made by enlarging the natural spaces that form around large roots. Rock crevices and hollow trees may also be used, and cones are sometimes stored under fallen trees or even in abandoned buildings. Green cones stay tightly closed all winter and well into spring in these humid spaces.

The white pine cones shown in the next image were also nipped by a red squirrel, and these cones probably look more like the ones you’re used to seeing. There must have been an interruption before they could be transported to a storage cavity, because they’ve dried out and released their seeds. Our weather has been dry lately, so drying may have happened unusually quickly, making the cones useless for winter food. So if the seeds were released when the cones opened, where are they, you ask? Such a concentrated serving of edibles wouldn’t have gone unnoticed by birds and small mammals and would have been rapidly consumed.

I was curious about how the squirrels detach cones from branches. I imagined a a lot of yanking and chewing, which should have left tooth or claw indentations somewhere around the sides of the cones. But when I looked for marks, all I could find were small bits of exposed wood at the attachment sites. The photo below shows the lighter separation areas at the bases of some of the red pine cones I examined. On Norway spruce and white pine cones it was the same– all I saw were small separation wounds at the bases.

I realized I needed to see how cones are attached to twigs, and what I found suggests that nipping cones is pretty straightforward. In the next photo you see a red pine cone attached tightly to a twig. A squirrel need only bite through the attachment point by inserting its tiny incisors into the angle between the cone and the twig. This would produce a lighter colored spot at the separation point like the ones I observed on the dropped cones.

Image from TheSpruce.com

I’ve never seen this happening (how I would love to levitate to the top of a tree and watch!) but I did find a video of a red squirrel harvesting cones from a western pine, probably a ponderosa pine. You can see it here. (The clearest view starts at 2 minutes and lasts about a minute.) The squirrel perches on the branch and works from the back side of the cone, occasionally using its front feet but mostly just gnawing at the connection between the cone and the branch until the cone falls.

Finding the evidence left by these frenetic little creatures isn’t hard–just pay attention to what’s on the ground whenever you pass under conifers. You’re most likely to find signs of harvesting where there are middens (piles of discarded cone scales and cores) from previous years, since resident squirrels tend to keep the same territories year after year. And sound may guide you to a harvesting site. A falling cone lands with a thump; the bigger the cone the louder the thump. If a falling cone hits branches on the way down you’ll hear some plunks and bonks followed by a thump. Follow your ears toward the sounds and you’ll probably find nipped cones scattered on the ground and a red squirrel chattering angrily at you from high in the tree.

River Otters: Living in Two Worlds

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

Photo by Scott Levine, Finger Lakes Land Trust

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

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

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

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

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

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

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

Getting to Know Porcupines

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

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

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

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

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

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

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

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

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