The coat changes color in winter. Mustela erminea occurs in the tundra and forest zones of North America, Eurasia, Ireland, Japan and the semi-deserts of USSR, Mongolia and North Africa. The short-tailed weasel is found in many habitats from tundra to deep forest but prefers areas with vegetative or rocky cover. The ermine is primarily noctural with a diet consisting of small rodents, birds, eggs, frogs and insects. The short-tailed weasel is swift, agile and has a keen sense of hearing and smell.
Adult males are dominant over females and young.
Females are polyestrous but produce only one litter per year. Mating generally occurs in late spring or early summer. Litter size averages 6 young.