Overall, these animals are thought to be live by themselves except when mating. The mountain weasel breeds once a year. Males fight for the females. The mountain weasel usually mate in February to March, and the young are usually born in May. The gestation period is 30–49 days. The mountain weasel gives birth to one to eight young ones. The young ones are blind, and their fur is not well developed. Lactation lasts about two months. After weaning, the young become independent but they still live with their brothers and sisters until fall. Young are able to breed in the next season when they are just under a year old.