Of equal importance to the fur is a natural body oil, which is spread throughout the fur by grooming. Grooming behaviors include barrel rolls in the water, as well as blowing air into the fur. Captive sea otters will groom each other, but this behavior is rare in the wild. Male and female sea otters usually segregate into separate groups. Male sea otters mate with several females throughout the year., usually bonding with one female for 3-10 days.
Females are able to bond with several males while in estrus, but one male is more common.
The duration of the estrus period coincides with the length of the pair bond, usually 3-4 days. Copulation always occurs in the water. The male usually floats on his back, holding the female on his belly. The female is also on her back, with her head tilted backwards, the male holds her in place by tightly gripping her nose with his teeth. This method often leaves the female's nose scarred and battered, a sure sign of recent copulation attempts.