The snow around the region this week is a blessing. For several members of our wildlife community, a forest floor that remains free of snow into December becomes problematic, as a dark background contrasts with their newly developed coat of pure white fur.
Among the creatures that change color in autumn as part of a survival strategy is a small, yet especially fierce predator – the short-tailed weasel, better known to trappers and backwoods sportsmen as the ermine.
In summer, the ermine has a thin, light brown coat that causes it to blend into any woodland setting. Additionally, the small size of this sleek carnivore, which is only slightly longer than a chipmunk, makes it difficult to spot as it quickly darts under clumps of leaves, beneath fallen logs and into crevices among rocks. Even though the ermine is an inch or two longer than a chipmunk, its slender body shape results in an average weight that is slightly less.
In early October, the ermine starts to grow its winter coat of long, dense fur. This process is triggered by a certain amount of daylight that occurs during the first weeks of autumn. Temperature is believed to have some impact on the rate of growth of its fur, yet it is the dwindling amount of light that seems to be the major environmental factor regulating the development of its winter coat. Cool weather that our region has experienced over the past several weeks has allowed the process of hair growth and color change to be completed on schedule, as the ermine, along with the long-tailed weasel and the varying hare, is now pure white, except for the black tip on its tail.
While the ermine is considered to be fairly common and widespread across the entire Park, the abundance of mice this past summer has given a boost to the population of this elusive predator. Even though the ermine is not substantially larger than a mouse, it regularly stalks and kills any small rodents it happens to encounter as it prowls the various nooks and crannies throughout its territory.
Because of the ermine’s long and lanky body shape, it dissipates heat at a faster rate than an animal that is plumper or more rounded in stature. While this is an advantage for an active animal in summer, winter can be extremely difficult. The ermine’s incessant need for food forces it to remain on the prowl for prey both night and day in order to maintain a suitable internal body temperature. It is estimated by researchers that the ermine must ingest roughly one-third of its body weight each day in order to avoid hypothermia and death. This is the equivalent of one healthy adult mouse, or two young mice or voles. The ravenous appetite of the ermine in winter forces it to attack a wide variety of ground-dwelling animals ranging in size from shrews to red and gray squirrels, which are substantially larger than the ermine.
Upon spotting a sizeable animal, like a varying hare or grouse, the ermine attempts to sneak up on its quarry and then pounce on the victim’s back, biting its neck and throat. With its set of sharp canine teeth and powerful jaws, the ermine is known to kill creatures that are many times its own body size.
The relatively small stomach of the ermine prevents this carnivore from ingesting large amounts of food after making a kill. Upon getting its fill of fresh meat, the ermine often drags any remains to a secluded spot in the hope that nothing else will find and eat it. The ermine may also pull a few dead leaves and other pieces of debris from the forest floor over the partially eaten carcass in an attempt to conceal it from other animals. If hunting is good, the ermine may never return to cached items, although during the winter in the Adirondacks, such frozen bodies can remain a viable source of food for several months.
Photo of Eermin in winter coat, courtesy Wikimedia user Steven Hint.
A version of this article first appeared on the Adirondack Almanack in November, 2012.