Sea Otter

Sea Otter



COMMON NAME: sea otter
KINGDOM: Animalia
PHYLUM: Chordata
CLASS: Mammalia
ORDER: Carnivora
FAMILY: Mustelidae
GENUS SPECIES: Enhydra lutris


DESCRIPTION: In appearance, sea otters are stouter and have larger ribcages, smaller tails and blunter muzzles than other species of otters. Yet, sea otters do possess the fine, dense fur coats characteristic of the Mustelidae. Their forefeet are small and dexterous with retractile claws and the flipper-like hind feet are broad and webbed. Juvenile sea otters tend to be a uniform dark-cinnamon brown while adults develop lighter gray or buff coloration on their heads.
MALE In general, mature male sea otters tend to be slightly larger than females of their respective subspecies.
SIZE: Alaskan sea otters are slightly larger than California sea otters
MALE Alaskan sea otters are slightly larger than California sea otters
FEMALE Female Alaskan sea otters measure up to 140 cm (55 in.) in length
MALE Mature male Alaskan sea otters weigh up to 39 kg (85 lb.), while California sea otters average 29 kg (64 lb.)
FEMALE Adult female Alaskan sea otters can reach weights of up to 33 kg (72 lb.), and female California sea otters weigh on average 20 kg (44 lb.)
DIET: A sea otter has a metabolic rate much higher than most mammals of similar size, and must consume large quantities of food. Adult sea otters may eat as much as 9 kg (20 lb.) of food each day. Among their food preferences are sea urchins, crabs, abalone, clams, mussels, octopus, and fishes. Most sea otters specialize in only a few types of the available food items.
GESTATION: Approximately 4-9 months with an average of 6 months; probably includes a 2-3 month period of delayed implantation
ESTRAL PERIOD The reproductive cycle in California sea otters is about 12 months. If a female's pup doesn't survive, she may experience postpartum estrus.
NURSING DURATION Approximately 6-8 months (wean)
MALE Approximately 5-6 years; usually don't actively breed for several more years
FEMALE Approximately 4 years
LIFE SPAN: On average, 10-15 years with some individuals living more than 20 years in zoological parks
RANGE: In coastal regions throughout the eastern North Pacific Ocean. Alaskan sea otters inhabit the coast of Alaska, including the Aleutian and Commander Islands. California sea otters are found off the coast of central California, from Half Moon Bay to Pt. Conception.
HABITAT: Typically found in coastal waters no further away than 1 km (0.6 mi.) from shore. The Alaskan sea otter has a greater tendency to haul out (come to shore) than the California sea otter.
POPULATION: REGIONAL The California population is still small - roughly 2,200-2,800 sea otters
STATUS: IUCN Endangered
CITES Appendix II (California subspecies is listed as Appendix I)
USFWS Overall, listed as threatened. The population south of Pt. Conception, CA is listed as Experimental Population/Non-essential


1. The sea otter's dark brown fur is the finest and densest of any animal fur. On an adult animal, there are an estimated 650,000 hairs per square inch. A sea otter relies on its fur to keep warm-it doesn't have an insulating layer of blubber as other marine mammals do. Natural oils in a sea otter's fur repel water and trap tiny air bubbles, providing a layer of warm air between the otter's skin and the harsh elements of its environment. Sea otters may spend as much as 48% of the daylight hours grooming their fur.
2. Sea otters sleep, rest, and usually swim by paddling with their hindflippers on their backs. California sea otters spend almost all of their time in the water, while Alaska sea otters often sleep, groom, and nurse their young on land.
3. Tool use is an unusual behavioral trait seen only in sea otters and a few other types of animals. An otter may remove an abalone by repeatedly hitting it with a rock. It also may use a flat rock to break open the shells of crustaceans and mollusks. While holding the rock on its chest, the otter pounds the animal on the rock until it breaks or opens.


Sea otters once were abundant along most of the coastal North Pacific Ocean. That was before fur traders hunted them for their thick, luxurious pelts. By the year 1900, sea otters were nearly extinct. Protected since 1911, Alaska sea otters have made a comeback.

Because they rely on their dense fur for insulation from the chilly ocean water, sea otters are particularly vulnerable to the detrimental effects of an oil spill. If a sea otter swims into an oil spill, its fur becomes soiled and loses its insulating qualities, allowing water to penetrate to its skin, causing hypothermia and ultimately, death.


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