Have you seen this critter?


by Susan Michaud

What is brown in the summer, white in the winter, and eats mice for dinner? If you said ermine, you would be right. The short-tailed weasel, also known as the ermine (Mustela erminea), is common in the mountains of Colorado, and area residents have spotted him many times romping, bouncing, and plunging through the snow.

His size and the length of his tail distinguishes the ermine from his larger cousin, the long-tailed weasel, who also lives in Colorado. The ermine is much smaller at 8- to 10-inches long and weighing in at one and a half ounces. The long-tailed weasel averages 14 to 18 inches and weighs around 5 ounces. While both of their tails are tipped with black, the long-tailed weasel’s tail is around one-half the size of his body while the ermine’s tail is much shorter.

During the winter, when the ermine is completely white, the black tip on his tail diverts predators such as the hawk or eagle. The bird will aim for the black tip and inadvertently miss the ermine’s body.

Always Hunting
The playful demeanor of the ermine may well be his way of hunting for his favorite dinner. The ermine’s main diet is the mouse and vole although he will eat an occasional chipmunk, squirrel, or rabbit. In the summer, he adds frogs, nesting birds and their eggs, insects, and berries to the menu. He has been known to eat chickens but will often visit a chicken coop just to feast on the rats and mice that are attracted to the chicken feed. According to the Colorado Parks & Wildlife (CPW) website, the ermine can take down an animal much larger than himself by wrapping his long body around the prey and killing it with a quick bite at the base of its skull.

Introduction of the ermine has been attempted to lower rodent populations, but the unintended consequences have been dire at times. According to Crittering.com’s article, “Tracking the Ermine,” posted on February 26, 2015, by James Beissel:

In the late 1800s, short-tailed weasels were introduced to New Zealand by European settlers in an attempt to control the rabbit population (also introduced).

The impact on New Zealand’s native ground-nesting bird populations has been disastrous. The ermine’s slender body can find its way into a rodent’s burrow, and he will live there until he has eaten all of the occupants. He will often kill more than he needs and cache the rest since he has a high metabolism and must eat one-third to one-half of his body weight each day. This is also why he hunts even during the coldest weather, although mostly at night.

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Who Needs a Cat?

Susan Shea, in her February 17, 2020 article, “Winter Weasels – White on White,” published at northernwoodlands. org, shared this story: My sister once lived in an old farmhouse that became infested with mice. She and her roommates had a contest going to see who could devise the most ingenious mousetrap, and they kept a tally of how many mice were killed. Then an ermine moved in with them for a month.

“We didn’t have much of a mouse problem after that,” she recalled.

A Kremmling local recently shared a similar story of her “no-good cat” killing an ermine that had been working rather successfully on her mouse problem.

Known the World Over
Known as “stoats” in other parts of the northern hemisphere, the ermine can be found from Russia and Scandinavia to Greenland, Japan, and Ireland. He and his fur have been popular for centuries. Wikipedia states:
Ermine luxury fur was used in the 15th century by Catholic monarchs, who sometimes used it as the mozzetta cape…. The ceremonial robes of members of the UK House of Lords and the academic hoods of the universities of Oxford and Cambridge are traditionally trimmed with ermine. In practice, rabbit or fake fur is now often used due to expense or animal rights concerns. Prelates of the Catholic Church still wear ecclesiastical garments featuring ermine (a sign of their status equal to that of the nobility). Cecilia Gallerani is depicted holding an ermine in her portrait, Lady with an Ermine, by Leonardo da Vinci.

Brown with a light-colored underbelly in the summer, the ermine mates during this time, and after a long delay in implantation of embryos followed by a gestation period of about 30 days, four to nine tiny young are born in April. The male and female do not live together but do live near each other. The male’s territory comprises many smaller, female territories, and the older the male, the larger his territory becomes.

If you are lucky enough to see one of these small critters in your travels, you can thank him for keeping the rodent population under control in your neighborhood.