Mating takes place once a year, in February and March, with females remaining in heat for about three weeks.

As the mating season approaches, males leave their territories and travel long distances in search of females. One male may mate with several females and each female may be mated by several males.

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How does this promiscuous mating behavior favor the strongest males? Experiments on mink farms indicate that when a female is mated by several males, it is the last mating which produces most of the kits. This suggests that in the wild, the males which father the most kits are the stronger ones which are still mating at the end of the season. Further supporting this notion is the fact that when the mating season comes to an end, the male mink stays with the last female mink it mated with.

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Fighting, which is common among rutting males, also favors the stronger animals.

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Seven to 30 days may elapse between fertilization and implantation of the egg, with gestation proper lasting 27-33 days. The average total gestation period is about 51 days, but young can be born as early as 40 days.

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The offspring, known as “kits”, are born in April or May. Litters range in size from two to 10, but five or six is typical. Newborn kits weigh about 6 gms and wear a short coat of fine, silvery-white hair. When they are about 2 weeks old, this coat is replaced by a dull, fluffy, reddish-brown coat. Kits are also born deaf and blind, gaining their hearing and sight when they are five weeks old.

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At eight to 10 weeks old and weighing about 350 gms, kits are weaned and begin to accompany the mother on hunting trips. Even though they are capable of fending for themselves at two months, kits stay with their mother until autumn when they leave to establish their own territories. At five months old, kits are as large as adults, but sexual maturity is not reached until 10 months.

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Despite the fact that mink have a fairly short life span in the wild, they are extremely prolific and capable of completely replacing their populations over a three-year span.

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