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North American River Otter

North American River Otters Running & Gliding

2-24-16 otter slide 142One 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

3-3-15 otter tracks IMG_5843North 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

1-30-14 otter slides  058North 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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Otter Holes

1-20-14 otter hole IMG_5577River otters are one of the most aquatic members of the weasel family. They can swim up to six or seven miles per hour on the surface of the water as well as underneath it, and can remain submerged for up to two minutes. Otters spend a great deal of time fishing under the ice, and obtain oxygen from open holes such as the one pictured (as well as from air bubbles under the ice). As their tracks indicate, otters come up onto the ice to eat their prey, be it fish or crayfish, their two favorite winter meals.

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More Otter Sign

3-1-13 crayfish IMG_3205It’s often a lot easier to find signs of otters than otters themselves. Recently I discovered two dead crayfish on the shore of a mostly iced-over pond that I knew was inhabited by otters. Nearby otter scat confirmed that these crayfish were probably left by satiated otters. The most important prey item in a majority of otter scat analysis studies is fish, followed closely by crayfish. Otters will take advantage of other prey, such as frogs, salamanders, ducks, muskrats, an occasional young beaver, mice, snakes, insects and even turtles when readily obtainable, but fish and crayfish are first and second choices.

Otter Slides

2-25-13 otter slide2 IMG_3773Otters will travel long distances from one pond to the next, and when they do, they frequently alternate between bounding and sliding. They often slide down hills, but they also slide on level ground, as in this photograph, and sometimes even uphill. While sliding, the otter holds its front feet back along its sides with its hind feet out behind it, leaving a trough roughly 6” to 12” wide and up to 25 feet long. Two footprints (actually four, but the hind feet land on top of where the front feet landed so it looks like two) can be found at the end and at the beginning of each slide, where the otter stopped sliding, bounded and began sliding again. You can see at least five separate slides in this photograph. Occasionally, in deep snow on level ground, an otter will use its foot to help push it along, either inside or outside of the trough. Otters slide at all times of the year, on mud as well as snow and ice, and appear to do so in order to get from one place to another, as well as purely for fun, as when they repeatedly slide down the same slope over and over. (Thanks to Mark and Susan Boutwell for sharing their discovery.)

Beaver & Otter Cohabitation

2-22-13 otter scat and beaver track2 IMG_3211It is not coincidental that you often find otters residing in beaver ponds. There appears to be a commensal (one animal benefits while the other is unaffected) relationship between these two animals. The beaver is unaffected – it is a herbivore, so its food supply is not threatened by the presence of otters. (While an occasional beaver is eaten by an otter, it is a rare occurrence.) The otter, on the other hand, benefits from abandoned as well as active den sites (both beaver bank dens and lodges) as well as an ample supply of fish due to the impoundment of streams by beavers. While I was aware that otters often take over abandoned beaver lodges, I only recently learned that the lodge does not have to be uninhabited for otters to move in. This was confirmed when I discovered a large amount of otter scat (mostly fish scales and crayfish shells) on top of a beaver lodge, right next to the hind foot print of a beaver. Freshly placed sticks on the lodge (it is in open water) indicated that it was occupied by beavers, while an otter’s stream of air bubbles could be seen as it exited the lodge and popped its head up above the surface of the water.