Enhydra lutris has a very unique life history and reproduction cycle.  Sea Otters have a polygynous mating system and show highly significant sexual dimorphism.  Sea Otters give birth throughout the year, there is three factors that may effect when the female gives birth those are:  the weather, amount of food available, and the location. Mating and breeding does not take place in the Sea Otter’s life until later on.  Females are not sexually mature until three years and males are not sexually mature until 5-6 years.  Neither of them breed successfully until at least 7 years.

A mother sea otter and her pup which is lying on her stomach.  Photo by Michael L. Baird

The process of reproduction begins with the male courting the female sea otter.  The male sea otters will swim around and search for females in oestrus .  When courting, the males tend to swim in a face down swimming posture, moving faster than normal.  When they are encountered by a female the male tries to embrace her or sniff her body.  If the female is interested a period of rolling around and playing goes on for some time.  If the male is rejected he is either pushed or shoved away.  The two will usually separate themselves from the group for a few days and this is when mating begins.

During mating the male grips his teeth onto the female’s nose and also wraps his forelegs around the female’s chest to hang on to her. During the reproduction cycle females get the nickname Rudolph because after mating the female’s nose is bloody red.  Mating only takes between 15 and 30 minutes.  These thirty minutes tend to be very vigorous and intense for both the females and males.

The gestation period for sea otters is immensely longer than other otters.  Their gestation period lasts between 4 and 12 months.   After fertilization takes place, the egg undergoes a number of changes.  As is moves down the fallopian tubes from the ovary to the uterus, it divides numerous times and then reaches a stage called blastocyst.  Next the sea otters go through a phase called delayed implantation and development is suspended for several months or days.  This phase usually lasts between two and three months.  Sea Otters give birth to their pup in the water and very rarely ever give birth on land. 

After birth the female watches her cub and grooms the pup’s hair on her chest for the first few hours.  New born otters are extremely helpless because they are blind and not very mobile.  The growth rate of the otter is very slow.  The first swimming attempts take place at about three months, but diving takes more time.  After four months they follow the female on nightly travels for food.  About 8 months after birth the pup begins to go out on its own and begins to take care of itself.

Female sea otters have an average litter size of 1 pup.  Occasionally the female may give birth to twins but the female only takes care of one of the pups and the other pup usually dies. Sea Otters may live for over 20 years when kept in zoos and other such places, but in the wild they tend to live between 10-15 years on average.