Posted by Janet Harriett on May.05, 2010

Photo Credit: Steve Hillebrand/ US Fish and Wildlife Service

In May, Wildlife Wednesday looks at unique mothering styles in the animal kingdom. This week, we look at what it’s like being a pregnant weasel and new weasel mother.

Long-tailed weasels use delayed implantation. Though the gestation period for a weasel is about 279 days (roughly comparable to a human), the baby weasels are only implanted and developing for 27 of those days.

After mating in summer, the weasel embryos develop for a couple of weeks, free-floating in the uterus. Following the short initial development, the female weasel “holds on” to the embryos, still free-floating, over the winter. The mother weasel establishes a den for birthing, lining it with the fur of mice and other prey animals. Often, the mother weasel simply moves into the den of a mouse or other prey animal.

In spring, the embryos implant and develop for the final 27 days so that the litter of 4-8 young is born in April or May, when food is plentiful and the young have plenty of time to develop hunting skills before winter.

Female weasels raise their young without help from the males. The young wean just a few weeks after they’re born, and eat prey the mother weasel brings back to the den until the young learn to hunt on their own. When the young are 7-8 weeks old, they leave the den and settle into their own nearby dens. They’ll establish their own territories as full-grown adults.

Female weasels born in May will mate that autumn and deliver their first litter when they’re about 1 year old. Male weasels reach maturity later and don’t generally mate until the spring following when they’re born.

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Posted under Living, Nature and Environment.