Little is known about the mating system in fishers. They usually breed in late March-early April. Egg implantation is then delayed for 10 months until mid-February of the following year when active pregnancy begins. After gestating for about 50 days, the female gives birth to 1-4 kits. Young are born blind and helpless in dens that are located in hollow trees. Kits begin to crawl after about 3 weeks and after about 7 weeks, they open their eyes. After 8 weeks they start to climb and are completely dependent on their mother's milk for the first 8-10 weeks. After that, they begin to switch to a solid diet. Males do not help raise their young. After 4 months, kits become intolerant of their litter mates, and at 5 months, the mother pushes them out on their own. Females reach reproductive maturity at 1 year of age, while males become reproductively mature when they are 2 years old.