This bold little carnivore is found throughout all of Canada, the northern United States, Europe and Asia. In summer, the ermine's coat is a rich chocolate brown above and creamy white below. The tip of its tail is black. In winter, the colour changes to white, except for the tail's black tip.
On average, males are 27 cm (10.5 in.) long, with a tail of another 7.5 cm (3 in.). Females are about 15% smaller. Ermine exhibit a high degree of size variation.
Muscular, agile and curious, they have been known to clamber up a person's clothing to reach food. They have also been known to attack humans when they feel threatened during an encounter, such as when an ermine is released from a trap. They are seen occasionally during daylight hours but are primarily active at night.
Some ermine appropriate the burrows of mice or ground squirrels and adapt them for their own use. Others build dens in hollow logs, under tree roots or in abandoned buildings.
The ermine's diet consists primarily of small rodents such as mice or lemmings, but it also preys upon larger species such as cottontails, small hares and porcupines, squirrels, pikas, rats, and even fish and birds. Some of this prey is probably consumed as carrion, and generally the larger males take the larger prey items. Ermines are hunted by coyotes, badgers, foxes, owls and wolverines.