Tag: porcupine

What Do Claw Marks Tell Us?

Claws, like hair and feathers, are made up of proteins called keratins and are characteristic of mammals, reptiles, and birds. In mammals claws evolved into a variety of forms, including fingernails and hooves, but it’s the hard, tapered appendages we consider true claws that are the focus of this post. The marks they make in tracks can tell us a lot about the lifestyles and behaviors of their owners.

The gray squirrel right and left front tracks in the photo below (direction of travel toward the left) show conspicuous claw marks. The tiny pricks made by the claws tell us they’re quite sharp, as we would expect in an acrobatic climber like a squirrel. Behind each claw mark is a toe impression, and behind the toes there is a tight group of middle pads. Two heel pads lie at the back end of the track. The combination of sharp claws and protruding toe, middle, and heel pads is what gives the gray squirrel its excellent climbing ability.

There’s another interesting feature in these prints: on the inner side of each set of heel pads there’s an impression of the vestigial fifth toe, something not often seen.

Porcupines, although not as graceful as squirrels, are also good climbers, and their feet are equipped with impressive claws. The photo below shows three sets of front and rear porcupine tracks, all heading toward the upper left. At the lower right you see a left rear track with a left front track above and to the left of it. Almost directly above those there’s a right rear print with a right front print above it. At the upper left there’s another pair of left front and rear prints. In each set the hind track is the larger of the two. The spaces between the claw marks and the oblong sole areas appear at first glance to be unoccupied– porcupine toes frequently don’t register in tracks. But if you look closely you can see faint toe impressions in the front tracks. You’ll notice that the claws of the front feet make marks a little farther forward compared to those of the rear tracks.

Fishers are also good climbers, so it’s not surprising that their tracks show the marks of sharp claws. The next photo shows the left front print of a fisher, oriented toward the left, with narrow claw gouges at the tips of the toes. But fishers don’t just use their claws for climbing–these animals are predators, and their sharp claws are essential for catching and subduing prey. The five toes, each tipped with a claw, make a lopsided crescent, and the middle pad and heel area make up the rest of the print.

Claws also come in handy for digging. Striped skunk tracks, like the left front print shown below, have prominent claw marks which extend well ahead of the toes. The claw impressions are more robust the ones in the first photo–not very good for climbing but hefty enough to make good digging tools.

The presence or absence of claw marks is sometimes considered diagnostic for track identification, but, like many aspects of tracking it’s not an absolute. The next photo shows front (lower left) and rear (upper right) prints of a gray fox, direction of travel from right to left. Gray foxes have semi-retractable claws, and prints without any claw marks, like the ones below, are common. The same goes for bobcats and house cats, which have retractable claws.

But if a gray fox needs extra grip it can extend its claws, making tracks that look like the ones in the next photo. The larger front track is on the right and the smaller hind track is on the left, and the direction of travel is toward the top. By extending its claws the animal was able to gain more purchase in the soft mud. The marks vary in thickness because of the varying depth of the tracks and movement of the toes, but the rear track shows slender grooves which are consistent with claws that are very sharp. Although not as arboreal as squirrels and fishers, gray foxes are good climbers. Their sharp claws assist not only in climbing but also in capturing prey. Claw marks are sometimes seen in feline tracks under similar conditions.

Animals with retractable and semi-retractable claws are able to draw their claws completely or partially inside their toes. But all animals, even those with robust claws, can control their position by flexing or extending the toes. The front track in the next photo (made by a coyote walking toward the left) shows beautiful impressions of the toes and the middle pad, but no claw marks.

A coyote moving at a side trot toward the right made the front (upper left) and hind (lower right) tracks in the photo below. Claw marks lie ahead of all four toes of the front track, and ahead of the leading toes of the hind track. The depths of the tracks made at the walk and at the trot are similar, but the toes were flexed enough at the faster gait to make most of the claws dig into the sand.

Partial sets of claw marks often occur in wild canines. The coyote front (left) and hind (right) prints (direction of travel toward the left) in the next photo show tiny pricks ahead of the leading toes, indicating that just the tips of the two leading claws in each print touched down.

Dog tracks, like the front print (direction of travel toward the right) shown below, are more likely to have blunt, robust claw marks that routinely show in tracks, even when walking or at rest. In the photo the claw marks have rounded leading edges due to their wider tips. In addition to the blunt claw marks, the more rounded overall shape and the outward angles of the inner and outer toes are indicators of domestic dog rather than coyote or fox.

To further drive home this point, contrast the dog print above with the red fox front track (heading toward the right) in the next photo. The red fox claw marks are slender and pointed, and they’re oriented straight ahead–or even slightly inward on the leading toes. The claw marks of the inner and outer toes are tucked tightly against the sides of the leading toes. It would be rare for a dog track to show this kind of compactness in soft mud.

There’s a explanation for the differences between the claws of dogs and wild canines. Coyotes and foxes spend their lives on the move, so their claws are constantly shortened and shaped natural abrasion. Dogs spend more time resting and less time travelling over the landscape, so their claws are not naturally worn down and must be trimmed manually. Consequently, the claws of dogs are usually longer and blunter than the claws of coyotes and foxes. Similarly, the feet of wild canines have excellent muscle tone, and this creates tracks that are tight and compact. The less fit feet of dogs spread out more and leave tracks in which the toes and claws often angle outward.

Cottontail rabbits and snowshoe hares have thick fur on the bottoms of their feet, so claw marks don’t usually show in tracks. In the photo of snowshoe hare tracks below, right and left hind tracks (oriented to the right) take up the center, a smaller left front track heading toward the left lies on the left, and part of a left hind track, also heading toward the left, can be seen at the upper right. The fur thins out somewhat in the summer, but even in July when these tracks were photographed, it was thick enough to muffle the claw marks in the rear tracks. They do show just a little at the tips of the toes in the front track.

But rabbit and hare claws are surprisingly sharp. Rabbits defend themselves with strong kicks, and the claws can inflict real damage. Claws also help the animals to grip the ground in the weaving and dodging escape maneuvers that help them evade predators. In the next photo you see two rear prints made by a leaping cottontail rabbit. The claws dug in deeply to give the rabbit a powerful take-off.

Why claw marks appear the way they do, why they’re present or missing, how they’re used by different animals–these are all questions that deserve our attention. Every track we find presents opportunities to explore this topic further.

Mud, Glorious Mud!

Unlike many people I know, I’m always sad to see the snow disappear for good. But as soon as I think of what comes next–mud season–I get excited all over again. The transition between the seasons is highlighted in the photo below. A gray fox had stepped in some mud and then left it’s muddy footprints on the snow as it walked from left to right. Each deposit of mud is made by first the front and then the rear feet from the same side, and the zig-zag pattern of the walk shows nicely.

Once the snow is gone, ordinary mud takes its place as a medium for recording tracks. In the next photo an opossum stepped in some mud at the edge of a puddle, leaving a collection of both complete and partially obscured prints oriented toward the left. At the upper left there’s a right front track with a right rear track just behind it. Farther to the right you can see part of another right front track. In the lower right corner there’s a nearly complete left front print and just the suggestion of a left rear behind it. The front prints show the five widely spread toes that are characteristic of the opossum. In the front print at the upper left the segments of the semicircular middle pad are especially clear. The rear track in the upper center shows the strikingly different form of the opossum’s rear foot: a thumb-like inner toe pointing inward and four additional toes close together and pointing outward.

One of the nice things about mud is that it can record the presence of animals that we don’t encounter during the cold season. A spotted salamander (or maybe two of them) walked through the mud in the next photo. These amphibians hibernate in winter and come out in early spring, so mud season is a good time to look for their tacks. There are two trips: one going from the left side toward the upper right and the other proceeding from left to right along the lower part of the frame. Each trail consists of a central drag mark made by the tail and a sequence of front and rear prints on each side. The patterns of the prints tell us that the animal(s) were moving at an understep walk, with each rear foot touching down just behind the front foot from the same side. In the lower trail you can see the difference between the smaller, four-toed front prints and the larger, five-toed hind ones.

The tracks in the preceding photos are pretty obvious, but it’s not always easy to spot tracks in mud. In the photo below there’s a patch of shiny mud in the center of the shot, and on the right side of that patch there are some tire tread marks. If you look on the left side of the same shiny mud toward the top you’ll see a red fox track. The animal was moving from top to bottom, and because there weren’t many muddy spots the print in the photo was the only one I could find.

The close-up below shows the same track, but in this view it’s oriented in the opposite direction, toward the top. The central mound typical of canine tracks can be seen, and the marks made by the hair on the underside of the foot show clearly. There’s even a partial impression of the bar in the middle pad.

Woodchucks, like salamanders, spend the winter below ground and often emerge just as mud season is beginning. The next photo shows the left rear track of a woodchuck at the upper left and a left front track at the lower right. The five clawed toes of the rear print show clearly–the middle three toes set close together and the inner and outer toes angled toward the sides. Behind the toes you can see the four segments that make up the middle pad. In the front track the four toes with their substantial claws can be seen. The subdivided middle pad of the front foot lies behind the toes, and the heel pads show as two depressions behind the middle pad. The front print has a curvature toward the inside, a trait typical of the woodchuck.

It takes a medium with a fine texture to show details of the tracks of very small animals, and what better medium than mud? In the photo below you see the tracks of a white-footed mouse bounding from lower left to upper right. The tracks are arranged in the typical rodent bounding pattern–two rear prints (in the upper right quadrant) that are widely set and almost even with each other. Behind the rear tracks, the front prints are set more narrowly and, in this case, slightly staggered rather than even with each other. Track details show beautifully, especially in the left rear (the topmost track) and the left front (farthest to the left). If we compare these tracks with the woodchuck tracks above we see the rodent family resemblance, especially in the rear prints. The symmetrical mouse front tracks are more typical of other small rodents than the curved front prints of the woodchuck.

You can’t ask for a better rendition of detail than the porcupine tracks in the next photo. Porcupines have unique foot anatomy: their tough, undivided soles have a pebble-like texture that gives the animals good grip when climbing. The photo shows a left front print and, just behind it and overlapping slightly, a left rear print. The tracks are heading toward the left, and the texture of the soles shows beautifully. Because the leading edge of the rear foot touches the trailing edge of the front track, the two tracks seem to be joined together. You may be able to pick out the claw marks of the hind print along the leading edge of the sole of the front print. The four claws of the front foot made indentations at the very left, and if you look closely there are marks made by the three outer phalanges of the front foot behind the claw marks.

Once the snow melts and the weather warms, mud may not last long. Puddles may dry up and wet areas may fill in with plant growth. But mud can also appear in new places, and abundant rainfall can bring on new mud seasons long after the early one is over. As a matter of fact, I found the porcupine tracks in the photo above in the month of July. So keep an eye on the conditions of the puddles in your neighborhood, and don’t be surprised if you come across some beautiful mud when you least expect it.

When the Snow Gets Deep

One of the challenges in a winter like the one we’ve been having is tracking in deep snow. Our native animals are mostly well equipped to cope with such conditions, but the evidence they leave can be mystifying–animals may change their habits, tracks and trails may look very different, and the details we generally rely on for identification may be absent. But the lives of animals are still written in the snow. To read these stories we just need to acquire some new reference images and expand our tracking skills.

A red fox made the trail shown below. In the deep snow the direct register walk was the most energy efficient gait, each hind foot coming down in the hole made by the front foot on the same side. Compared to walks in easier conditions the fox’s steps were shorter and its trail width was greater. The animal lifted its feet cleanly out of the snow, leaving just a few drag marks.

The direction of travel, from bottom to top, is revealed by the sprays of snow which fell off the feet as they rose out of the holes and moved forward. Whether animals are walking or moving at faster gaits–as long as their movements are regular and smooth–snow falling from their feet usually lands ahead of the tracks. Only during sudden acceleration or changes of direction do we see snow pushed backward or to the side.

A coyote walking from left to right made the trail in the next photo. The snow was less consolidated so there’s a softer appearance to the trail. The details in the track floors are obscured by the snow that fell in as the feet were lifted out, and the animal’s feet skimmed the soft surface leaving drag marks. Looking down into the holes (which is always a good idea in this kind of situation) we can see the shapes of the forward edges of the animal’s feet. The overall shape of a coyote’s foot is oval or egg-shaped, but how should we describe just the front half? The best I could come up with is parabolic or bluntly arched. Whether or not there’s a word for it, this shape is characteristic of coyotes and red foxes, and also some dogs. And there’s another feature that is typically canine: in the very tip of the hole on the right you can see two small dents made by the leading claws–a dead giveaway for a red fox or coyote. Gray foxes usually have more rounded leading edges and less tendency to show claw marks. Being shorter legged than red foxes, gray foxes are more likely to leave drag marks, and dogs are also prone to dragging their feet.

These two trails illustrate the general appearance of canine trails in deep snow. Because walks in deep snow tend to be very close to direct register it may be possible to get rough measurements for track widths, and this, plus stride or step length, can help to separate coyotes from red and gray foxes.

Bobcat trails in deep snow may be quite different from canine trails. In the photo below a bobcat walked from bottom to top, and at each step it spread its feet as they went down into the snow, creating a sequence of interlocking triangles. As usual, snow obscured the details of toes and pads at the bottoms of the holes, but in the lowermost impression you can see that the forward edge of the track is widely crescent-shaped rather than parabolic.

Sometimes animals negotiating deep snow move faster, perhaps out of fear or maybe just playful antics. In the photo below a red fox bounded from upper left to lower right, leaving holes where its body went in up to its shoulders. There may not be much information inside the holes, especially if the snow is loose and movable as it was when the photo was taken, but their width provides a rough measure of the width of the animal’s body. The level of effort required for this kind of movement means that it can’t be sustained for long periods, so following the trail either backwards of forward will probably bring you to a change of gait.

In spite of their long legs, deer are not well suited for moving in deep snow. Their feet are small in proportion to their body weight, so they sink in deeply. Deep drag marks like those in the photo below are typical, and sometimes the tips of the toes can be seen at the bottoms of the holes.

In deep snow deer may limit their movements to trails they’ve already made, such as the one in the next photo, where they can move with less effort. If the difficult conditions persist the animals may limit their movements to very restricted areas which become crisscrossed with trails. These deer yards are usually found under conifers, where the snow isn’t as deep and the evergreen foliage traps heat. When deer yard up the available browse is quickly eaten, so they eat very little, reduce their activity, and wait out the winter.

For short-legged animals like porcupines, skunks, and muskrats the only option in deep snow is to bulldoze their way through. In the photo below a skunk struggled from upper left to lower right, its body plowing through the snow and its feet punching deep holes in the bottom of the groove. The small pits made by the feet, combined with the short strides and wide trail width are good indicators of the animal’s identity.

When temperatures fluctuate or sun melts the surface, snow can develop an icy crust. Sometimes this reduces the problem of movement, allowing lighter animals to move easily over the surface. But if the hardness of the crust varies or the animal is just a little too heavy, we may find scenes like the one in the photo below. A coyote attempting to cross a drift found that it wasn’t always supported by the crust. Where it broke through it left crisp outlines of its lower legs and spread toes.

Like other animals, rabbits and squirrels can plunge deeply into snow, and this can make it hard to identify their tracks. But the difference in the positioning of the front feet usually provides a clue to the animal’s identity. The next photo shows a cavity made by a gray squirrel bounding from lower left to upper right. Inside the hole there are two depressions, each one made by a front foot and a rear foot from the same side. The wide separation of the depressions and the equally wide entry and exit disturbances give the hole a boxy or rectangular shape.

Compare that to the next photo of a rabbit in deep snow, also bounding from lower left to upper right. Because the rabbit brought its front feet down on or close to the center line of the trail, the entry point (at the lower left) is narrow. The rear feet made a wide depression in the deepest part of the hole and left separated drag marks coming out. The result is a triangular cavity with the wide end opening toward the direction of travel.

Maybe the biggest hinderance to learning how animals move in deep snow is just getting out into the stuff. You’ll need snowshoes or skis, or at the very least good gaiters, to get close to the tracks. But if you spend some extra time arranging all your gear you’ll be rewarded with a deep look into the lives of animals in deep snow.

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.

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.