River otters in Alaska breed in spring, usually in May. Mating can take place in or out of the water. One to six pups (usually two or three) are born the next year any time from late January to June following a gestation period of nine to 13 months. Delayed implantation (a period of arrested embryonic growth) accounts for this variation in the length of gestation.
The pups are born toothless and blind in a den that is
usually a subterranean burrow. Their eyes open seven weeks
later. When about two months old, they begin to leave the
den and shortly thereafter start to swim and eat solid
food. They are taught to swim by the female who must coax
or drag them into the water. Pups are weaned when about
five months old. They will stay with their mother until
shortly before her next litter is born.
River otters are sexually mature when they are two years
old. A female will then mate with the male of her choice
and produce one litter each year. Otters can live and
breed for more than 20 years.