River Otter Tails
From their nose to the tip of their tail, North American River Otters measure three to four feet long. Their tail makes up anywhere from a third to nearly a half of their length. A River Otter’s tail is very thick at its base, packed with muscles, flexible, and tapers to a point. It is used to steer when an otter is swimming slowly, propel the otter when it is swimming at high speed and to help the otter balance when it stands upright on its hind legs. River Otters, known for their powerful swimming, can reach speeds of six to seven miles per hour with the help of this appendage.
When loping through the snow, River Otters often hold their tails up off the surface of the snow, but not always. Occasionally drag marks can be seen. In the accompanying photograph, an otter had leapt up an incline, and in so doing left an imprint of its impressive tail in the snow.
(Thanks to Alfred Balch for photo op, and Joan Waltermire for her sharp eyes.)
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North American River Otters Sliding
There is no denying that North American River Otters know how to travel and have fun in winter. Whether on a flat surface such as a frozen pond or river, field, or down slopes, otters take advantage of the snow, bounding then dropping to their belly and sliding, saving precious energy. Most slides are relatively short, around 10 feet long and 6-10 inches wide, though they can be as long as 25 feet long on slippery ice. At the beginning and end of a slide there are tracks (from where they push off with their hind feet, and cease sliding and begin bounding again), creating a dot-dash pattern. Sometimes a downhill slide is used repeatedly and when it is, bobsledders have nothing over otters, as water from the otters’ coats creates an icy and very slippery slide.
For those of you who would like to view an excellent video of an otter sliding, go to https://www.youtube.com/watch?v=iBB0OLOkvIU .
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River Otter Brown-out
River Otters have latrines on land where they come to defecate, urinate and roll around, all in the same area. This area is used over and over and is referred to as roll or brown-out. The latter name is derived from the fact that much of the vegetation dies as a result of the urine and acid build-up. Most otter scat (also referred to as spraint) disintegrates fast and consists of piles of fish scales, with little form. However, if you come upon a recently-visited brown-out, or if the otter has consumed prey other than fish, such as crayfish, tubular scat can be present (see photo insert). Look for River Otter brown-outs on narrow strips of land that stick out into ponds, or a strip of land between two bodies of water. (Thanks to Squam Lakes Natural Science Center for rolling otter photo op.)
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Young Otters Just Beginning to Explore Outside Their Den
Between February and April, female North American River Otters give birth to an average of two or three young inside their dens, which tend to be near water, usually in an excavated cavity under tree roots, logs or thickets. Occasionally they have been known to give birth in abandoned beaver and muskrat lodges as well as woodchuck burrows. The mother doesn’t allow her young to exit their den until they are three or four months old, which, for the oldest litters, is in May. At this point, after their waterproof adult coats have grown in, she begins to teach them how to swim (surprisingly, this skill is not innate). The mother continues to be very protective and secretive, hiding and shielding the young (even from their father) until they are about six month old. Thus, glimpses of young otters are not likely to be had until late summer, and only then if you’re lucky. (Photo: adult river otter. Thanks to Heidi Marcotte and Tom Wetmore for photo op.)
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North American River Otters Running & Gliding
One hundred years ago, naturalists were puzzled by the disappearance of otters in the winter. Some people theorized that they must be hibernating, but in fact, otters are active throughout the year — they just aren’t observed as often in the winter as in the summer. Because they inhabit water, where the fish that they eat are found, and often reside in bank dens (above water level), otters can spend most of their winter under cover of ice. However, some do travel over land from open water to open water, upon occasion. In fact, it is not unusual for them to cover several miles in their search for an open stream or a spring. Run and glide, run and glide, often along a frozen river or marsh, but also through the woods, where otter tracks seem so incongruous. Paired foot prints stop and start each slide; this combination is a dead giveaway as to who is making grooves in the snow. Ultimately, if you persevere when following them, you will find that these slides disappear into open water.
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Otter Tracks
North American River Otters have four webbed feet and strong claws that assist them in water as well as on land. There is relatively little hair on the soles of otter feet, and therefore the individual pads are often well defined in good tracking snow. Each foot leaves a five-toed track, with the inside toe on the front feet being somewhat smaller than the others. Otters have four plantar pad glands in the center of each hind foot with which they mark mounds of vegetation they create.
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Otter Ingenuity
North American River Otter tracks are usually found where otters have travelled from one body of water to another. In the winter, this can be on frozen streams as well as over land. If they come to an incline, even a small one, they often take advantage of it by letting gravity do the work on the way down. In this photograph, two otters travelling together had the same idea at the same time, and reached the marsh at the bottom of the hill by effortlessly sliding down the hill on their bellies, leaving two 12-inch-wide grooves in the snow. Although John James Audubon, in the mid-1800s, observed a pair of otters sliding down an embankment over and over 22 times, stopping only when they discovered that they were being observed, the otters that made the tracks in this photograph were intent on getting where they were going, and only slid down once.
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