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Animals I Have Known #10

Weasel or is it an Ermine?
by Dan Hartman

Dec. 5, 2011

Probably one of the most misunderstood creatures of the forest is the weasel. Like the wolf and other predators, it is always portrayed as the villain in children’s stories. This is probably because they are so seldom seen. And if they are it’s just a quick glimpse, making it hard to determine how they go about their day-to-day life. So instead we expand on what we know. Their killing ability.

I must admit though, most of their lives are consumed with hunting. Their long narrow bodies covered with short hair loses energy quickly and so they must constantly refuel. Hunting can’t always be good, so they must often return to caches made when hunting was successful. This is why they kill more than they can eat.

For example we butcher a cow knowing we cannot possibly eat it in one sitting. We put the remainder up in a freezer to be used when needed. A weasel does the same thing; only his freezer is a hollow log, a cave in a rock pile or maybe an underground burrow. Years ago I followed an ermines tracks that showed he carried a mouse. It eventually disappeared in a hole in a log. Months later I returned and split open the log. Inside I found mouse hair and entrails. He had returned.

Life expectancy for weasels is very short. Two years for females and one for males, with seven years being the maximum on record. Owl, hawks, martens and foxes are his deadly pursuers, but starvation is his biggest enemy. Oddly one of the main causes of death is from a parasite carried by shrews, which is one of the little mammals main prey species.

Some time ago we had a large ermine move in to our woodpile for the winter. He soon had an under snow burrow system that covered our yard. One hole just outside our bedroom window seemed to be his favorite and we spotted him there often. In those days I had a lot of time and no money, so I began changing the setting around this hole. One day he would emerge under a pine bough, another in an aspen forest and so on. We even put a lipstick camera there and got footage for Jeff Hogan’s Geo film, “Yellowstone Wild”. We also had a marten frequenting our cabin that year and we could tell by the tracks it was after our ermine. In a shot I’ll always wish I had category, I was photographing our little guy one morning when something behind him caught my eye. I looked up from my camera to see a marten five feet away approaching catlike. In a flash the ermine was into his snow burrow. The marten stood frustrated again. It was then I realized I hadn’t fired a shot! A couple days later the ermine had two scratch marks on his side we took to be from an encounter with the marten. When spring came we were lucky to still have the ermine and were fortunate to see his transformation back to weasel. It started with a brown spot above his eyes. In the coming days the brown spread to his back and down his sides. At the end of a week to nine days he was in complete summer coat.

In a study done to determine what triggered a weasel’s coat to change to white, five weasels were captured up north. Two were taken to the far south. The three remaining in the north changed to white when it turned cold. The two in the south did not change, as it never got cold enough.

Only short-tailed weasels are called ermine when they change to white in winter. It’s taken from the French word for weasel “hermine”. However everyone, including me, refers to long tailed weasels as ermine when they have turned white. I’ve actually only seen a handful of short-tails in my 30 years of living in the high mountains. Long-tails are a common occurrence.

The next time you catch the blur of an ermine bounding through the snow understand he cannot stop and visit. The little fella just does not have the time!


View slide show


Ermine Changing To A Weasel

Now It's A Weasel

Short-tailed Weasel With A mouse

Great Horned Owl With An Ermine

Weasels Can Climb