Least weasels enjoy a very wide distribution. They are naturally found all over the northern hemisphere in Canada, the northern parts of the United States and some of the eastern US. All parts of Russia, Europe, and northern Asia have least weasels; they have been introduced to many other areas including northern Africa and multiple islands.

Least weasels are fierce predators. A reputation that is shared by many mustelids such as ferrets, otters, wolverines, badgers, etc. They are well-known for taking on prey up to 5 times their size.

Most commonly they catch mice and mouse-like rodents like voles. But they have been known to take bird eggs, lizards, frogs, salamanders, fish, worms, and carrion.

 In order to maintain their body temperature and high metabolisms, they need to eat at least 50% of their body weight each day.  Compare that to a big cat which needs to eat 1/3 of their weight in a week and you begin to realize why least weasels have to be good hunters.

Scientists discovered that their metabolism is even higher than their rodent prey. With a heart that beats 400 times per minute, they are not able to hibernate. During the winter, they have to hunt even under the heavy snow.

This voracity has been key to their success as predators. It pays to catch anything they can and as much as possible because food shortages can and do occur. If a least weasel comes across multiple rodents, they will kill as many as possible and stash the surplus in other den sites to feed on later.  If they don’t eat the surplus within a few days, it often spoils and they will leave it because they prefer fresh food.

This may seem wasteful but there is another hidden benefit. By bringing rodents underground; when they die, their bodies decompose and fertilize the surrounding area.  In the winter, it is a life saver since the food will not spoil as fast and help weasels get through lean times.

Despite their small size, least weasels live much longer than other animals of comparable stature. In the wild they usually only survive a year or two. But in captivity they can live up to 8 years. Mice even in captivity usually only live 1 or 2 years.

Compared to other carnivores least weasels are a bit of an anomaly when it comes to pregnancy and rearing their young. A dog and cat’s gestation period lasts around 65 days, and both puppies and kittens are alert with their eyes open and are exploring their environment at 4 weeks of age.

Least weasels on the other hand have a 35-day gestation and their kits don’t even open their eyes until they are 1 month old.  At 12 weeks, they are independent. That is a very long time for such a small animal to develop. For example, mice are completely independent at 4 weeks. So why do least weasels take so long to grow up compared to other predators and animals of similar size?

It’s all in the body shape as female weasels can’t afford to bulge during pregnancy since they would not be able to fit in tight spaces. This causes them to essentially give birth to premature babies, and then spend more time raising them outside  in the real world.

When they are being raised, it is exclusively by the mother. After mating, the males will, leave the area.

Once the family does break up at 12 weeks, each weasel will stake out their own territory, with the male’s being larger than the female’s territory. Often, one male’s territory will encompass several female territories. For such a small animal, they can live in a relatively large area. Some territories are up to 40 acres in size for a single male least weasel.

They have been quite successful for such a small mammal and are found all over the northern hemisphere. It is believed they crossed the Bering Land Bridge around 200,000 years ago into North America.

Least weasels also don’t build their own burrows, they steal it from their prey. After they have consumed the residents, they use the rodents’ fur to line the new den. It may seem macabre, but it is a genius use of resources and keeps the weasels comfortable in the winter.