Tuesday, December 3, 2013

Adirondack Wildlife: The Short-Tailed Shrew

Short Tailed shrewThe powdery layer of snow covering the forest floor across the Adirondacks is still too thin in many areas for back country skiing and snowshoeing; however, several inches of fluff is ideal for noting the tracks of wildlife. Among the most common of mammals that populate the Park is a miniature predator, whose tracks typically appear from beneath an old stump, a rotted log, a surface boulder or a pile of brush and zigzag in an erratic pattern for roughly a dozen feet before disappearing under some other chunk of debris.

In our mixed forests and woodland edges, the short-tailed shrew is a prolific, but rarely seen, member of the wildlife community, yet its abundance becomes evident by the presence of its tracks in the snow, especially in late autumn and early winter before an increased snow depth reduces this creature’s visits to the surface.

The short-tailed shrew is the largest species of shrew that exists in the Adirondacks, as this animal is only slightly smaller than a mouse and is larger than either the northern water shrew (which was profiled in a Nov. 20th article), or the pygmy shrew (which was written about in July of 2012). The short-tailed shrew gets its name from its short, stubby tail which, like a lemming’s, is less than one-quarter the length of its body. The short-tailed shrew also has the dubious distinction of being the only venomous mammal in the Northeast.

Like other shrews, the short-tailed shrew primarily a preys on any and all small animals that exist on the forest floor. In summer, insects, worms, spiders, centipedes, slugs and other invertebrates that live in the layer of organic matter on the forest floor comprise the bulk of this animal’s diet. Should this shrew happen to encounter a mouse, immature chipmunk, vole, another type of shrew, or a bird probing the ground for food, it quickly attacks and attempts to bite its victim, introducing a mouthful of toxic saliva into its quarry. With its exceptionally keen sense of smell, the shrew then follows the scent trail left by the wounded animal and eventually comes across the carcass of the recently expired animal. Even though the shrew is smaller than the critters it bites, the ravenous appetite of this creature allows it to devour the remains within a day or two.

The venom of the short-tailed shrew is only fatal when introduced into the body of small vertebrates, as its effectiveness is greatly reduced on much larger organisms. Not only are there no reports of a human having a fatal encounter with this shrew, but the only instance of this predator biting a person that I have ever read about concerned a researcher handling a specimen taken from a live trap. Because of a shrew’s exceptionally keen sense of smell, this mammal is quick to detect an unconscious person in a sleeping bag on the floor of a lean-to or tent, and immediately vacates the scene.

As winter progresses, this shrew spends most of its time nosing about the nooks and crannies among the layer of frozen leaves, sticks, pieces of bark and other items on the forest floor in its search for dead or dormant invertebrate matter and occasional seeds. Even though the shrew has a taste for fresh meat, this insectivore eats sunflower seeds. Tracks of a shrew may occasionally be noted beneath a bird feeder, as this creature searches for seeds spilled from above.

As temperatures continue to get colder, and the snow depth increases, shrews make fewer trips to the surface. A good blanket of fluff forms an ideal layer of insulation that keeps the frost line from penetrating too far into the soil and allows a favorable subnivean microhabitat to develop, in which this creature can prowl for food. The decrease in surface visitations can be noted by the absence of shrew tracks as the season progresses. However, like all creatures that live under the snow, shrews do periodically come to the surface for a breath of fresh air and to get some exposure to daylight.

Around my feeder there currently are both mouse tracks and shrew tracks. The tracks produced by mice inevitably leave evidence of their lengthy tail, however the tracks made by a short-tailed shrew seldom show that it has such an appendage. Mice also tend to stay on the surface better than shrews, which sink more into light powder and often show evidence of their underside dragging across the surface.

The presence of a light layer of snow can send Nordic enthusiasts to the local golf course or athletic field for an early season outing on a pair of rock skies. The die-hard naturalists however, always takes to the woods when several inches accumulate on the ground, as track patterns in the snow provide a wealth of information on the local fauna.

Photo: A short-tailed shrew (courtesy Wikimedia user Gilles Gonthier).

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Tom Kalinowski is an avid outdoor enthusiast who taught field biology and ecology at Saranac Lake High School for 33 years. He has written numerous articles on natural history for Adirondack Life, The Conservationist, and Adirondack Explorer magazines and a weekly nature column for the Lake Placid News. In addition, Tom’s books, An Adirondack Almanac, and his most recent work entitled Adirondack Nature Notes, focuses on various events that occur among the region’s flora and fauna during very specific times of the calendar year. He also spends time photographing wildlife. Tom’s pictures have appeared in various publications across the New York State.

2 Responses

  1. John Jongen says:

    I marvel at this shrew’s lighting-fast speed and their obvious tenacity. I have observed them sharing the same territory with chipmunks and grey and red squirrels for some three decades. They are entertaining to watch whenever they make a rare appearance. Got to love them with their closed eye lids and cuddly-soft downy fur.

  2. Charlie S says:

    By looking at the photo I would’ve thought this shrew was much larger had you not described it.What a beautiful animal!All animals are beautiful!

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