Sea Otter

Enhydra lutris

Classification

Kingdom: Animalia

Phylum: Chordata

Subphylum: Vertebrata

Class: Mammalia

Order: Carnivora

Family: Mustelidae

Subfamily: Lutrinae

Genus: Enhydra

Species: Enhydra lutris

Description:

Males are larger than females, weighing up to 45kg and a length of up to 1.5 m. Females come in at 33kg and up to 1.4 m in length. This makes the Sea otter the largest member of its family, Mustelidae. They have long hind legs with large webbed feet and short forelimbs with retractable claws. The Sea otter has a relatively short tail that is less than one third of their total body length. Their pelt is brown to reddish brown and they have a light tan head. Their fur is the densest of all mammals with approximately 100,000 hairs per square inch of skin. This adaptation is critical because the Sea otter does not have any fat for insulation; therefore their dense fur is what protects them from the frigid waters they inhabit.  

Subspecies Distribution:

There are three subspecies of E. lutris, these are Enhydra lutris lutris is found in the Japanese island chain of the Kuril Islands north to the Commander Islands, Enhydra lutris nereis is found off the coast of central California, and Enhydra lutris kenyoni is found in Alaska and the Aleutian Islands.

Habitat:

Sea otters are known to make their homes in Kelp forests. They inhabit cold coastal marine waters, hence the name Sea otter. They usually are found in Kelp forest ecosystems because of the protection that the forest provides against predators. They also do not stray far from the shore, staying less than 1 kilometer from the coast.

Behavior:

Although mostly solitary, the Sea otter males will group together when resting. The Sea otter will spend their lives in the water, leaving the water only to rest when otter population density is too high. They use their hind legs and tail to swim with a dolphin type motion and hold their front legs close to their bodies. Sea otters are active during the day and forage for food more during dawn and dusk; dives last any where from a minute to 6 minutes.  Foraging is done with touch from the nose and front paws. When prey is located, the Sea otter will grab the prey with its front paws and take it to the surface. Once at the waters surface, Sea otters will roll onto their backs to eat their prey. When they bring food up that has a hard shell or external covering, the Sea otters will use a rock to break open their prey; the same rock is often used for many feedings. Sea otters also wash there food before consumption. During the night the Sea otter will wrap itself in kelp when sleeping to keep from drifting.

Diet:

Being carnivorous, Sea otters will consume any thing they can get ahold of. Invertebrates such as mussels, clams, sea urchins, snails and abalone are very common as well as octopus, squid, crab, sea stars, and even fish are eaten by Sea otters. Generally Sea otters will eat what is most available to them at the time in their area. Water is attained by drinking sea water but mostly from the food that they eat. Sea otters must eat 20% to 25% of their body weight every day.

Reproduction:

Polygamy is the name of the dating game in Sea otter society. Males will have territories with females that inhabit their territories and the males will defend their territories ferociously with vocalizations and splashing; fights between males is very rare. The males mate with females in estrus and will bond with the female during her estrus period, which is only 3 days. During mating the male will hold the females snout in his mouth; this will leave scars on the female. In the Aleutian Islands May through June, and along the coast of California January through March, has shown to be a popular birthing time for the Sea otters but they do reproduce year-round. Sea otters perform delayed implantation which makes for a rather uncertain gestation period but gestation periods are about 4-12 months long. The Sea otter give birth to only one pup at a time that weighs 1.4 to 2.3 kg. Pups remain with their mothers for 5 to 6 months. Sea otter pups are cared for by their mothers and will nurse until weaned but begin consuming solid foods after birth. The mother teaches the pup to swim, forage, and groom and any other social behaviors. The pups usually stay with the mother for up to 8 months. Males will reach sexual maturity later than females at about 5 to 6 years of age, females at 4 years of age.

Predators:

Sea otters must be wary of predators at all times; killer whales often claim Sea otter pups that stray from the kelp forest and also adults. Sharks also pose a threat to this species and of course humans. Polluted waters disrupt the delicate kelp forest ecosystem and without that ecosystem the Sea otter will not survive.

Ecological Role:

Sea otters would not exist if it was not for kelp forest, and the kelp forest would not exist if it wasn’t for the Sea otter. Sea otters are what is called a keystone species. The survival of the kelp forest ecosystem depends on the Sea otter and its eating habits. Sea urchins are the otters favorite food and kelp is the sea urchins favorite food, so the Sea otter plays a critical role of controlling the population of animals like the sea urchin that graze on the kelp.

The Fur Trade:

In the mid 1700’s through 1911, Sea otter pelts were a hot commodity. A single pelt could bring 1125 dollars; luckily this no longer legally occurs because of the International Fur Seal Treaty that was established in 1911. There are four countries under the treaty, U.S., Russia, Japan, and Great Britain.

 Status:

In 1972 the U.S. Marine Mammal Protection Act was established which aided in further support for the Sea otter. The main threat that the Sea otter is facing is the possibility of an oil spill. There is currently 2200 California Sea otters and it is thought that a single oil spill could wipe out the entire population. This subspecies is listed as threatened under the Endangered Species Act, and is listed under CITES Appendix I. The other two subspecies are listed under CITES Appendix II. The IUCN lists Enhydra lutris as an endangered species.

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  Sea otter info at Animal Diversity Web

  Sea otter info at EnhancedLearning.com

  Friends of the Sea Otter

For more information contact the Small Carnivore TAG Education Liaison

Website Created By

JamesFernandez

Pensacola Junior College, Zoo Animal Technology Program 2005