Outdoors in the Land O'Lakes - January 19, 2012

Turncoats: Weasels in Winter

By: Lorraine Julien

A small white face pushes up through the snow, its small black eyes gleaming. The long slender body comes next. It is probably one of the three main species of weasels that inhabit our area. They are: the Short-tailed weasel (Mustela erminea), the Long-tailed weasel (Mustela frenata) and the less common Least weasel (Mustela nivalis). These little fellows are very similar, except for their size, but the most striking thing they have in common is the fact that their fur coats change color twice a year; once the shorter days of autumn approach, the chocolate brown fur on their upper bodies changes to snow white over the course of just a few weeks. As the days grow shorter, less light enters the weasel’s body through its eyes, stimulating moult by means of its pituitary gland. Temperature also plays a role in this change. A second moult as the days grow longer, reverses the colour change. Mother Nature is amazing!

The winter-white version of the Long-tailed weasel has recently been spotted in our area. Perhaps there is a greater abundance of mice this year since we haven’t noticed them before (mice are their favorite meal – in fact they are probably the world’s most efficient mousers). You may spot a weasel investigating holes, logs or bushes in its quest for food. Every now and then it will lift its head, stand upright to check out the surroundings, then tear off again zigging and zagging at top speed to deter predators. The long thin body humps in the middle much like a caterpillar’s. Small birds, moles, voles, eggs, snakes, fish, worms, insects and even some young bats are also fair game. With such a varied diet, I doubt these aggressive carnivores would ever be on an endangered species list.

You’d think that hard-working chipmunks would spend the winter snug and cozy in their little tunnels. This is not always the case: if weasels can squeeze their heads into a burrow or hole, then they can enter and kill the residents. Rabbits, rats and squirrels larger than themselves are killed by weasels pouncing on their prey with clawed forelegs and then finishing the victim by biting the back of the neck.

The ferocious Short-tailed weasel (sometimes called Ermine in winter) is very quick and agile. It can weigh up to 3.7 oz. (105 g) and can be up to 13” (34 cm) in length (a third of which is its tail). With a slender, almost serpentine body, it can easily move through small burrows in nocturnal pursuits of rodents. It is also a good climber and chases squirrels and chipmunks into trees. The Ermine in North America ranges from the northern U.S. to above the Arctic Circle. This weasel survives by killing what it can, when it can, then storing surplus in a side tunnel of its den (usually dead mice). Ermine in northern countries, including Canada, were once trapped for their luxurious, snowy white fur though demand for these pelts is much lower now and hence fewer animals are trapped.
The Long-tailed weasel is similar to the Short-tail but larger and more powerful. It can weigh up to 9.4 oz. (267 g) and be up to 22” (55 cm) long including a tail up to 6” (15 cm) long.
The little Least Weasel (Mustela nivalis) also goes through the color change. It is the world’s smallest carnivore weighing between one and two oz. (up to 57 g) and hardly longer than 9.5” (25 cm) including its tail (not much bigger than the mice on which it preys). Its speed and ability to crawl into tight spaces helps it to avoid predators. Unlike the other two weasels, its tail does not have a black tip.

All weasels are lightning quick hunters but, if they feel trapped, as a last resort, they can emit an odor said to be as pungent as that of the striped skunk – the only difference (and consolation!) is that it cannot spray the musk as skunks do.

Weasel predators include coyotes, foxes, hawks, owls and sometimes humans. Farmers who raise chickens and rabbits probably do not want to have these aggressive carnivores around – for the rest of us though, they certainly reduce the rodent population.

Please feel free to report any observations to Lorraine Julien at naturewatching@gmail.com or Steve Blight at natureobservations@rogers.com