Weasels

by Judy Radovsky

There are two weasel species found in the Pacific Northwest and both have the same basic physical conformation—long, lithe, slender bodies with small heads tapering to bluntly pointed muzzles. Both species have short legs and small, sharp, curved claws on each five-toed foot. The short-tailed weasel, Mustela erminea, (also called the ermine) is between 7.25 and 13.5 inches in length, including tail, and weighs one to three ounces. Its tail is usually less than half the length of the head and body. The long-tailed weasel, Mustela frenata, ranges in length from11.25 to 22 inches, including tail, and weighs between four and 11.5 ounces. The tail is more than half the length of the head and body in this species.

The weasel's fur is short and fairly fine. The upper parts are chocolate brown with a darker face mask and black tail tip. The underparts are white, from chin to crotch and down the insides of the hind legs. The long-tailed weasel tends to a lighter brown pelage on top, and cream to dark yellow underparts. Both species, in higher elevations, molt to a winter coat in October-November. They become all white, retaining only the black tail tip.

Weasels prefer to live in forested or wooded areas. The long-tailed weasel is more likely to be spotted by humans, as it will roam about in open grassy areas. The short-tailed weasel rarely leaves the protective cover of fallen trees or thick brush. Female weasels breed in July and August--they have delayed implantation, so that the embryos don't implant and develop until eight weeks before birth the following April or May. Average litter size for both species is six to eight.

Weasels build dens in hollow logs, rocky crevices, or will take over rodent burrows. They eat mainly rodents and other small mammals, as well as birds, eggs, frogs, and insects. They are cunning and ferocious hunters, able to maneuver easily through narrow burrows or grapple with larger prey aboveground. They generally kill with a bite to the back of the skull. Prey is often carried back to the den for consumption. It is common for weasels to chew through the skull to eat the brains of their prey. They will also rip the fur from their mammalian prey and push it into the walls of their nest. This eventually creates an enlarged and heavily insulated den.