An online resource based on the award-winning nature guide

Weasel Family

Otter Holes

1-30-19 otter hole img_5596A pond can have one to two feet of ice on top of it, yet North American River Otters somehow manage to find a way to come up through the ice. How do they do this? Careful observation reveals that the ice where otter holes are found is thinner than most of the pond’s ice. Otters rely on spring-fed open water and areas of thin ice for surfacing holes. Here they break through the ice and often drag larger fish out onto the ice to eat them.

If otters are feeding in a beaver pond and they can’t find openings in the ice for fishing, they have been known to tunnel into beaver dams for access to open water. In late winter, water levels sometime drop below the ice, leaving an air space that lets otters swim and hunt beneath the ice without the need for holes. (Look closely at opening to see the actual hole beneath the surface water that they emerge from.)

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The Sniff Test

1-30-19 red fox marking img_7153When your quest is to find out as much as you can about the identity, activity, diet and territory of your four-footed neighbors, it is logical to make the most of all your senses. Tracks can be seen, scrapings and bite marks on a tree can be felt and yes, one’s sense of smell can enhance any tracking expedition. Just as the tracks and scat of different species of animals have distinctive characteristics, so does the urine of different animals. Scent marking, including urination, is a behaviour used by animals to identify their territory, and therefore a highly visible sign in winter.

At this time of year, foxes are breeding, and without even putting your nose near where a fox has marked his territory with urine, you can detect its skunk-like odor as you pass by. If you’re so inclined (and I realize many readers may not be) you can heighten your sensory experience as well as your identification prowess by sampling the smell of other animals’ liquid waste. White-tailed deer urine has a pungent, piney smell, quite pleasing to this naturalist’s olfactory receptors. You can detect a porcupine den from a considerable distance by the pungent, very distinctive but hard to describe odor of its urine (which spills out onto and coats the bark of a tree den, thereby advertising the porcupine’s presence). Coyote urine smells very much like a domestic dog’s, and members of the weasel family often have musky-smelling urine, though a recently-sniffed fisher marking had very little scent.

Needless to say, it’s a lot easier to discover and sample urine when there’s snow on the ground and it is more evident. Virginia opossums, snowshoe hares, red and gray squirrels, eastern coyotes, red and gray foxes, raccoons, fishers, mink and striped skunks are all in or entering their breeding seasons, when scent marking is more frequent. Snow is currently on the ground, at least in northern New England. It’s prime time for olfactory activity, if you’re game. (Photo: stump marked by a red fox)

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Mink and Fisher Tracks

1-16-19 fisher and mink tracks img_2238As members of the weasel family (Mustelidae), Fishers and Mink have five toes on both front and back feet. Often all five digits do not register, but in prime tracking snow, you can sometimes see them. Typically, mink tracks are found near a body of water, and fisher tracks are found under a canopy, not in the open. Where you have both water and trees, it’s possible to see signs of both animals.

In general, the larger the animal, the larger its tracks. Mink weigh one to three pounds; fishers four to eighteen pounds. In this photograph, the mink tracks (smaller, in the middle) are heading towards the top of the photograph, and the fisher tracks (top most and bottom most) are heading towards the bottom of the photograph. They were both traveling on a frozen woodland stream.

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Distinguishing Small Weasels

12-21-18 ermine_U1A8001New England has two small weasels: Long-tailed and Short-tailed.  Both of these predators molt twice a year, from brown to white in the fall, and white to brown in the spring.  The name “Ermine” can refer to either of these two species, but it is most commonly used when referring to the Short-tailed Weasel.

Telling the two species apart can be challenging. Long-tailed Weasels are the larger of the two (head to tail = 12-14 inches), while Ermine are slightly smaller (head to tail = 7-13 inches).  Unless you have both species in front of you, however, their size is hard to assess.  A more helpful distinguishing characteristic is the length of their tail relative to their body length. Long-tailed Weasels have a tail longer than half their body length with a black tip. Ermine have a tail length which is around a third of their body length — it also has a black tip. (Photo:  Ermine (Short-tailed Weasel). Thanks to Sharon and Chad Tribou for photo op.)

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North American River Otters Foraging For Fish

11-30-18 otter with fish_U1A2403

Whether or not North American River Otters made the original holes evident in Wednesday’s Mystery Photo, they were responsible for keeping them open by frequently poking their heads up through them for some air. Congratulations to Noel K. for being the first to correctly identify their surface holes.  This was a tricky Mystery Photo, as there were none of the usual signs of otter activity (tracks, fish remains, etc.) on the ice surrounding the holes.  This is probably because the ice was too thin to support the weight of an otter.  To find the most humorous response, scroll down on Wednesday’s Mystery Photo comments until you get to Peg Emerson’s.

These semiaquatic members of the weasel family are active year-round and while they are mainly nocturnal and crepuscular during the summer, they are frequently spotted during the day in winter.  If otters encounter open water, they rarely resist the urge to enter it and pursue resident fish.

Thanks to their webbed feet and streamlined body, otters are accomplished swimmers and divers. They are able to reach a depth of around five feet and remain submerged for up to four minutes as they hunt underwater. Top swimming speed is seven miles per hour. (They can achieve a speed of up to 18 miles per hour when running and sliding on snow or ice.)  While fish are their mainstay, these carnivores also consume frogs, snakes, turtles, insects, birds and bird eggs and the occasional mammal (mainly muskrat).  Though called “river” otters, they forage in fresh, salt and brackish waters. (Thanks to Rita and Dave Boynton for photo op.)

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A True Mystery Photo

11-2-18 flying squirrel tails_U1A1190A discovery recently brought to my attention has stumped this naturalist.   What you are looking at is a collection of Flying Squirrel tails lying within a 30-square-foot patch of ground adjacent to a stand of Eastern Hemlocks. For several days in succession, additional tails appeared each morning, eventually totaling 20 or more.

Flying Squirrels, both Northern and Southern, are part of many animals’ diet.  Among the documented predators are Great Horned Owls, Barred Owls, Screech Owls, Northern Goshawks, Red-tailed Hawks, Martens, River Otters, Weasels, Fishers, Red Foxes and Bobcat.  Many of these animals can gain access to the trees where the Flying Squirrels reside.  Others take advantage of squirrels foraging on the ground.

The puzzling part of this mystery is the large number of tails.  In cold weather (usually in winter, but we’ve had below-freezing nights recently), Flying Squirrels huddle together in tree cavities in an attempt to provide themselves with added warmth.  Did a foraging Fisher discover a communal den?  How did it manage to capture so many squirrels?  Did the survivors remain in the same cavity, only to be captured in subsequent nights?  So many questions that this naturalist cannot answer. Perhaps a reader can! (Thanks to John Quimby and Michael O’Donnell, who kindly shared their fascinating discovery with me.)

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Fisher Landing

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Although capable of climbing trees, Fishers spend most of their time on the ground under dense woodland canopy. In the winter Fishers constantly leave sign while traveling two to three miles a day in search of squirrels, shrews, mice, voles, porcupines, hares and grouse, among other things, to eat. Beds at the base of trees, small saplings bitten, rubbed and rolled on, scat and urine marking – all are quite commonly encountered when following Fisher tracks. The Fisher sign I find quite elusive and therefore very rewarding to come upon is the imprint they make when they land in the snow after jumping down from a tree they’ve climbed. (Photo: landing imprint)

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