Gestation lasts from 20–31 days, and results in the birth of up to 11 young, although four or five are more typical. They develop their fur by 16 days, and open their eyes after around 3 weeks. They begin to leave the nest after around 30 days, and are sexually mature by the time they complete their second hibernation. Compared with similarly sized mammals, they have an unusually long lifespan, and have been reported to live up to 12 years in the wild.