Tag: muskrat

Muskrats: Life in Two Worlds

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

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

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

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

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

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

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

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

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

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

Streamside Discoveries

As the high water levels of late winter and early spring subside, stream and lake margins become interesting tracking locations. Water is a magnet for wildlife, and visiting creatures leave the evidence of their activities along the shoreline. A great blue heron left the collection of tracks shown in the photo below. The feet of herons resemble the feet of songbirds, with one backward-pointing toe and three forward-pointing toes. But unlike most songbirds, the toes of herons don’t all meet at one point. There’s a left print (facing toward the lower right) in the upper left corner of the photo that shows this nicely. The junction between the backward-pointing toe and the inner forward-pointing toe lies to the left of the intersection between the two outer toes. Another way of saying this is that the two outer forward-pointing toes join a little to the outside of the center of the foot. The same asymmetry shows in the right track in the lower right corner.

The spotted sandpiper is another bird that patrols stream and lake margins. These small birds–about the size of a starling–search for invertebrates on the edges of streams, ponds, marshes, and other bodies of fresh water. Their tracks (shown in the next photo) reflect their erratic and meandering movements. The three forward-pointing toes are relatively symmetrical and diverge at wide angles. On the back of the foot there’s short spur oriented to the inside that may or may not make an impression in tracks. The left print just below the stick in the upper right corner shows the spur nicely.

Raccoons prefer comfortable surfaces so it’s no accident that the animal that left the tracks shown in the photo below stepped along a soft deposit of sand left by a recent flood. The raccoon moved from the upper right to the lower left, leaving tracks in the sequence right rear, left front, left rear, right front. The difference between the wider but tighter rear track and the narrower, more spreading front track is easily seen in the set of prints at the upper right. Raccoons habitually work the edges of streams and ponds where they find tasty shellfish, frogs, crayfish and other invertebrates. The pattern of alternating sets of hind and front tracks from opposite sides tells us the animal was moving at a pace-walk.

Mink are also in the habit of travelling along the margins of water bodies. The animal that made the tracks in the next photo was moving from right to left at a lope, and the track sequence is right front, right rear, left front, left rear. Like raccoons, mink have five toes on both front and rear feet, but it’s not uncommon for the impression of the inner toe to be missing. In fact the only print in the photo that shows a clear inner toe is the left front. This track also shows the middle pad protuberances (just behind the toes) and the heel pad (the small indentation behind the middle pad). Mink share a taste for crayfish, frogs and invertebrates with raccoons, and occasionally catch small fish. They’re adaptable predators and may also hunt for small mammals on the surrounding land.

The mink’s larger relative, the river otter, also leaves its tracks along the edges of ponds and streams, but for this creature it’s mainly a matter of convenient travel between feeding areas. I found the tracks in the photo below on the inside of a bend in a stream where an otter had taken a short cut across a large sandbar. The sequence of tracks is the same as that of the mink tracks in the previous image, and the family resemblance–both mink and otters are mustelids–can be seen in spite of the different substrates. Otters are more aquatic than mink and capture most of their food in the water.

When they’re not foraging in the water otters spend their time on conveniently accessed sites near the water. They roll on soft surfaces like grass and forest duff to clean and dry their fur, and they socialize with other members of their family group. They also leave notices in the form of scat to non-resident otters that the territory is occupied. The otter scat in the photo below contains crayfish shell fragments, but it’s also common to find scats containing fish scales and bones, or the slimy remains of frogs. Otters often use latrines where scat of various ages and contents can be found.

The beaver is another very aquatic mammal. In the photo below you see two beaver tracks, a right front (above) and a right rear (below), both facing toward the right. In the front track the four toes show clearly and the two heel pads appear as elongated grooves because the foot slipped in the mud. In the bottom part of the frame the three outer toes of the hind print show clearly but the two inner toes are obscured by the front print. As is often the case, the webbing of the hind foot doesn’t show. The size difference between the front and rear tracks is striking and helps us to understand why beavers are such strong swimmers. Beavers feed on the leaves, bark, and stems of woody plants year-round, but during the growing season the diet also includes aquatic plants, cattails, sedges, and forbs. Their tracks usually lead between the water and foraging sites on land, and signs of branches being dragged into the water are common.

Smaller–but just as well adapted to life in water–is the muskrat. Like the beaver, the muskrat has rear feet that are much larger than the front. In the photo below, the track farthest to the left is the right rear, and just to its right you see the right front. On the right side of the frame the left rear lies below the left front. Notice that the small inside toes of the front feet made impressions in both of the front prints. The muskrat’s front feet, like those of the beaver, are adapted for handling food items and building materials rather than for swimming.

If you wander along shorelines you may find muskrat latrines. These sites are usually located on logs or rocks that lie in the water but protrude above water level. In the next photo you can see a rock decorated with scat of varying ages, deposited as an announcement that the territory is occupied. Although muskrats occasionally consume animal foods they are primarily plant eaters, and their scats usually contain fibrous material.

This is just a sampling of some of the wonders to be found along the margins of lakes, streams, and marshes. There’s always something to be discovered, so next time you’re out and about, take a detour to check a stream edge or a muddy shoreline. Better yet–if you don’t mind some wading–try a stream walk. It could be just the thing on a summer day.

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.