Most river otters (both male and female) become sexually mature around the age of 2-3; however, most otters do not reproduce until they are older, normally between the ages of 5-7 (Griess, 1987).  When they do reproduce it is seasonal reproduction (Liers, 1951). Female river otters are normally only in estrus for a single month of the year, and male otters are capable of reproduction for three months of the year (Stephens, 1957). North American river otters are polygamous (Stephens, 1957). The North American river otter has delayed implantation; this is very rare in otters shared only with the sea otter (Liers, 1951).  Fertilized eggs can remain in diapause up to 10 months before implantation.  Reproduction normally occurs during the late winter and early spring.  The average gestation period is between 65-75 days and the total duration of pregnancy is around 300-350 days on average (Stephens, 1957).

Offspring of the North American River otters are called kits.  On average there are normally 2-3 kits per litter (however, there can be up to 6 kits born at a single time!) (Stephens, 1957).  At birth the kit normally weighs only 4.5 ounces (Liers, 1951).  At this time they are unable to swim, they will be unable to swim until around two months.  The otter kits tend to leave their mother at around a year of age (Liers, 1951).


For a better idea of what these otters look like, visit our Gallery page.