The female rears the young alone. Litter size is reported to range from two to six but is most often three, and the young are born in March or April, eight or nine months after mating. This is an abnormally long gestation period for a small mammal and results from a phenomenon known as delayed implantation. After mating and fertilization, development of the embryo stops at a very early stage. Implantation into the uterus wall does not take place until February.
Delayed implantation occurs in several other members of the mustelid family as well.
The young are born in a den, usually located inside a hollow tree. At birth, they weigh about 30g, are blind, and are covered with a very fine fur. The female nurses the young well into the summer, spending little time away from the den until the young leave with her in June or July. Raising the young is an extremely energy-demanding task, and the female may lose considerable weight during this period. The kits apparently stay with their mother until late August or September, when they disperse.