An online resource based on the award-winning nature guide

Weasel Family

Mink Exploring Streams

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The pattern of diagonally-paired tracks indicates that it’s likely that a member of the weasel family has been travelling on top of this mostly-frozen stream.  The presence of water makes it likely that a Mink made them. For the most part, Mink are restricted to forest cover and ponds, streams and rivers. When bounding, their hind feet register almost exactly where their front feet were, creating this double-print pattern.

Many members of the weasel family, including Long-Weasels, Ermine (Short-tailed Weasels), and Fishers, also make these paired tracks, especially in deep snow. Size is one way to discriminate between them, with the size of Mink tracks (1 ½”-long) falling in between 3″- long Fisher tracks and 1”- long weasel tracks.

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River Otter Tails

3-31-17 otter tail impression2 026From 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

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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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Classic Fisher Sign

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Fishers are one of the most rewarding mammals to track as they leave so many signs. One of the most common ones, other than their tracks, is their scent posts. This is where a fisher rubs itself, anointing the substrate with its scent as it marks its territory. Young saplings often serve this purpose. The fisher rubs and rolls on a young tree, often a conifer, usually breaking a few branches.

If you see a scraggly-looking sapling in the woods, and there are fisher tracks nearby, examine the sapling closely for fisher hairs that often get caught on the branches when a fisher rubs against them. More often than not, the fisher will also mark the tree with a bit of scat or some urine. Fishers are very adept at controlling the amount of feces they leave, often excreting very small portions as markers throughout their travels.

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Fishers Climbing Trees

12-19-16-fisher-tracks-up-tree-049a2363If you look at the tree in the center of the photograph, you may be able to detect paired tracks in the snow along the length of its trunk.  As luck would have it, a fisher chose to ascend the one tree with snow still clinging to its trunk. Fishers are members of the weasel family and are well known for their ability to climb trees.  They do so in order to reach den sites as well as to catch prey. Fishers’ arboreal adaptations include semi-retractable claws and ankle joints that rotate so that they can descend trees head-first. Smaller females appear to be more adept in the trees than the larger males.

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Fishers Crossing Logs

11-25-16-fisher-tracks-049a1848The first snow that sticks on the ground is cause for celebration, if only because it allows you to know so much more about what goes on in the woods and fields that surround you than you would know if it never snowed. At this point the snow isn’t deep enough to distinguish tracks very well in the leaf litter, but thanks to the fisher’s propensity for crossing logs (which are relatively smooth, an excellent substrate for tracks, and retain scents well), one resident’s presence was announced loud and clear recently.

Fisher have large, wide feet with five toes on each foot and semi-retractable claws. This makes them well adapted for walking on snow, climbing trees and grasping and killing prey. (They are also capable of rotating their hind feet nearly 180 degrees, which allows for a headfirst descent from trees.) Their track is very distinctive, and can be quite common in forested areas of the Northeast.

Usually, if given the option, fishers will choose walking on a log over walking on the forest floor. Why would they have developed this preference? There often is no water where this occurs, so it’s not done in an effort to avoid wet feet. My best guess as to the purpose of this behavior is scent-marking. Fishers have been observed sliding along logs on their bellies, as they rub the scent of their anal glands along the top of the log. The fisher scent-marks with cheek, abdominal, neck, flank, and plantar (feet) glands, in addition to anal glands. A fisher leaves its scent with every step of its hind feet, and if rotting logs are superior scent-absorbers, it may be why fishers choose them over the forest floor.

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Young Otters Just Beginning to Explore Outside Their Den

e-river otter 125Between 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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