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Sea Otter Enhydra lutris

Sea Otter Behaviour

Feeding, Hunting & Foraging Behaviour of the Sea Otter

Sea otters eat mostly marine invertebrates but also dine on other animals that they hammer, tear, pick or snatch from the seabed during brief dives. Among the diet are sea urchins, mussels, crabs, abalones, worms, fish and their eggs, and octopus.  The sea otter stays close to shore where it will commute several kilometres to feed. Most of their food is taken in water less than 30 meters deep. The daily routine in California involves alternate snooze and groom bouts with a feeding bout. A feeding and grooming bout begins at sunrise and lasts for several hours followed by snoozing until mid afternoon when a second feeding bout occurs. Resting follows until about midnight when a third feeding bout and slumber. This routine is followed closely each day and seems to be only disrupted by storms. In Alaska, the routine is probably different especially in winter where they spend up to 70% of the time feeding. Otters open prey items by cracking the shells with their flattened molar teeth combined with hammering against a rock balanced on the belly. They also use rocks underwater to hammer shellfish free from the seabed. The sea otter is well known for its ability to limit the distribution and abundance invertebrate prey. They have been described as keystone species for their ability to influence the presence of other species in an ecosystem.


Aggressive, Defensive & Territorial Displays of the Sea Otter

Sea otters are highly sociable animals that form rafts of tens to a few thousand individuals. Rafts of males are the largest; female groups seldom exceed 30 animals. During the breeding season, adult male otters defend territories against other males. In California, these territories are about 40 hectares. Young males leave groups of females and pups soon after weaning to establish their own territories. Adult females tend to stay close to where they were born seldom traveling more than 50 kilometers. They will seek out males during the breeding season.


Sea Otter Courtship & Breeding Behaviour

Female otters become sexually mature when they are about 3 years old. When they enter estrus, females will swim to male territories where they briefly reside while they are mating.  Males without territories reside in rafts with females where they attempt to find mates, likely with low success. Male territorial otters approach females in estrus by nuzzling them that leads to fondling if a female is interested in him. After about an hour of this behavior, pairs will attempt to mate. She takes up a rigid position on her back while the male positions himself below her by holding on with his paws in her armpits and her nose in his mouth. Nose biting is painful and likely stimulates release of her unfertilized egg.  These bites can lead to bleeding wounds that form into distinctive scars. Most Russian otters breed in June and July, and September and October, Alaskan otters breed in September and October, and California otters breed from July to October.

Gestation takes about six months and a single pup is born. Twins are unusual and triplets are rare: among 1360 fetuses examined, 5 were twins, 1 was a triplet, and the balance were singletons. The pups are usually born in water at any time of year in California but mostly in January to March, most probably in April to July in British Columbia and Alaska. Birth takes place at sea although there are records of sea otters giving birth on land. Pup birth weight is about 2 kilograms. Pups are groomed extensively at birth to dry the fur. Suckling bouts last about 9 minutes and occur about 6 times a day. Sea otters, and particularly mothers with pups, spend most of their time floating in kelp canopies. Sea otters rarely come ashore.

Captive-raised otter pups begin to dive when they are a month old.  At 6 weeks it begins to eat food, they can swim on their back at about 8 weeks, and at 12 weeks, a young otter is capable of prolonged dives with its parent. Pups are independent at about 6 months of age. Mature females can reproduce each year. Male otters are sexual maturity at about 5 years of age.

Sea otters, and particularly mothers with pups, spend most of their time floating in kelp (macrocystis) canopies. 


Sea Otter Calls & Vocalizations

Marianne Reidman and her co-workers identified  ten types of vocalizations that they describe as screams, whines, whistles, squeals, whimpers, squeaks, hisses, growls, coos, and grunts. The calls are mostly for short-range communication among familiar individuals. 














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