Overview

Key Features:

Dark brown, dense fur, often with lighter coloring on head. About 1 m long and an adult weighs about 70 lbs.

Primary Common Name:

Southern sea otter

General Grouping:

Whales, seals and sea lions, otters

Geographic Range:

Half Moon Bay to Santa Barbara, California, and San Nicholas Island

Enhydra lutris nereis can be found in nearshore waters of the North Pacific, from Japan to the coast of the Kamchatka Peninsula, east throughout the Aleutians, and south through the Gulf of Alaska and along the Pacific coast of North America to Baja California, Mexico.
Maximum Depth: 100 meters or 333 feet

Notes:

Generally found in areas shallower than 40 m.

Habitats:

bay (rocky shore), bay (sandy shore), estuary, exposed rocky shore, exposed sandy beaches, kelp forest, protected rocky shore, protected sandy beaches

Notes:

Enhydra lutris lives in a variety of coastal habitats generally in areas shallower than 40 m. They are found most often in areas with rocky coastlines, where the sea bottoms are most diverse and where there are thick kelp forests. They can also live in sandy areas, among barrier reefs and in intertidal areas. While they mostly occupy shallow waters, they can travel through much deeper water when moving between foraging areas or during seasonal dispersal. Otters can dive up to approximately 100 m maximum depth, but for most females 40 m is the deepest (with almost all dives under 25m) and for most males 80 m is the deepest.

Abundance:

Relative Abundance:

Common in Monterey Bay.

Species Description:

General:

Enhydra lutris is the only species with in the genus Enhydra. Both the genus and species name mean otter. They belong to the family Mustelidae, shared with weasels, skunks and river otters. They are the only exclusively marine member of this family and the heaviest of all otters. Enhydra lutris is also the most aquatic species in the order Carnivora and is easily distinguished at the water's surface floating belly-up grooming or resting. They infrequently haul out on land or ice and females even give birth and nurse their pups in coastal waters. Of the marine mammals, they are the most recently evolved for life in the ocean.

Scientists recognize three subspecies of Enhydra lutris, one in California and two in Alaska. Otters ranging from northern California to Baja are called Southern or California Sea Otters and referred to as the subspecies Enhydra lutris nereis. Those that range farther north are called Alaska Sea Otters and there are two subspecies. E.l. lutris ranges from the Commander Islands in the western Bering Sea along the southeast coast of the Kamchatka Peninsula, through the Kuril Islands, and south to northern Japan. E.l. kenyoni ranges in the Aleutian and Pribilof Islands east to the Alaska Peninsula, into Prince William Sound, and along the coasts of southeastern Alaska, British Columbia, Washington and Oregon.

Distinctive Features:

Enhydra lutris is large relative to most other mustelids and has a short broad head and a short blunt snout. The subspecies in Alaska are significantly larger bodied and more robust than those in California. Enhydra lutris has a well developed upper lip and cheeks that are densely covered by stiff whiskers. The hindpaws are large, flipper-like and webbed and the forepaws are rounded. Enhydra lutris will use its forepaws like hands to manipulate food, groom and hold various tools for breaking open shellfish. The tail is long, flattened and oar-like. They have eight pairs of teeth in both the upper and lower jaws.

The body is completely covered by a dense coat of fur, except for the pads on the bottom of the fore and hindpaws and the tip of the nose. The fur consists of two layers, a dense underfur and less dense, but longer, fur consisting of guard hairs. The adult's coat of underfur may be dark brown to reddish-brown. While the less dense and longer guard hairs can be lighter brown to blond, particularly on the face and head. The guard hairs, when clean, are waterproof, protecting the underfur which traps a layer of air to provide insulation. Newborn pups have a light, buff-colored pelage with the guard hairs becoming yellowish several weeks after birth.

River otters, Lutra lutra may occasionally occur in marine habitats but can be distinguished from Enhydra lutris by behavior and physical features. Enhydra lutris differs from Lutra lutra in its large, flipper-like hind limbs, dorso-ventrally flattened tail, and flattened molars. Also Lutra lutra generally swims or floats on its bellies in the water, whereas Enhydra lutris almost always floats and mostly swims at the surface on its back.

Size:

At birth <em>Enhydra lutris</em> is 55-60 cm in length and weights 2-2.25 kg. Males can grow to a length of 1.48 m and a weight of 45 kg. Females can grow to a length of 1.4 m and a weight of 33 kg.

Natural History:

General:

Enhydra lutris is not very social and typically occurs alone or may form small groups of a dozen or more, called rafts, where food is abundant and kelp beds are thick. They are often seen floating on their backs, entangled in the thick kelp when resting or grooming, with their legs held aloft and their head raised. This position ensures they will not drift away and also exposes them less to the cold water. Heat regulation is important for these otters since they lack blubber and must maintain their dense fur in order to stay warm. Their fur is the densest of all mammals with up to 100,000 hairs per square centimeter. In order to maintain cleanliness and ensure the waterproofing, insulating quality of this thick underfur, they must spend several hours a day grooming. In grooming, they rub themselves with their forepaws to keep their fur fluffy with heat-insulating air and to coat their fur with natural oils from their skin and can also be seen rolling and somersaulting. A high metabolic rate also help maintains their body temperature. To maintain their fast metabolism, the average Enhydra lutris consumes a quarter of its weight in food daily or the equivalent to 2.5 tons of invertebrate biomass annually. Enhydra lutris is a diurnal animal, spending most of its day foraging and grooming.

Enhydra lutris swims at the surface on its back using strokes of its flippers and vertical movements of its flattened tail. However, surface swimming is energetically expensive, so on dives, they and swim at twice their surface speed if they vigorously undulate their bodies in addition to paddling. The front flippers have pouches of skin underneath them that are used to temporarily store food collected during extended dives to the bottom. Due to the flexibility of their wrists, these otters can fairly easily carry objects between their paws and forearms or between both paws. In fact, they use their forelimbs dexterously for eating, grooming and caring for their young. They are also among the few animals that habitually use tools. When they dive to the sea bottom, they will use rocks to retrieve abalone by smashing its shell and at the surface to break open mollusks and crabs. Enhydra lutris always closes its nostrils during dives and dives typically last only about 90 seconds. The heavy whiskers on the sides of it nose and important sense organs that can be voluntarily extended forward to feel and are likely used when diving in poor visibility conditions.

Enhydra lutris males live to 15 years, females live to 20 years. Adult males segregate from the rest of the population during most of the year and are avoided by females outside of breeding periods. The home range and migration of Enhydra lutris is likely dependent on availability of resources. Home ranges may be as large at 5.4 square kilometers, with most animals traveling found within 1-2 kilometers of the previous day\\\\\\\'s location. While adults are not vocal, pups are and their high-pitched, piercing calls to their mothers are loud and often audible for a hundred yards or more, even in areas of heavy, noisy, surf.

Enhydra lutris once thrived from Baja California, Mexico to the Pacific Northwest even through Alaskan and Russian waters and into Japan. But in the mid-1700s humans began hunting otters for their dense fur. Populations were reduced to the point of extermination in many parts of their historic range. And by 1911 the world population was estimated to be just 1,000-2,000 individuals. Although this species is still considered endangered, the otters have since been legally protected, and reintroduction efforts have shown positive results. The California population has grown from a group of about 50 survivors off Big Sur in 1938 to just over 2000 today.

Predator(s):

Enhydra lutris is preyed upon by sharks and Orcas, Orcinus orca.

Prey:

The diet of Enhydra lutris includes crabs, lobsters, urchins, clams, abalone, snails, mussels, scallops, chiton, cephalopods, and other invertebrates as well as some fish.

Feeding Behavior:

Carnivore

Notes:

The diet of Enhydra lutris varies according to the physical and biological characteristics of the habitats in which they occupy. In rocky-bottom habitats, otters generally search out and eat large-bodied prey, such as lobsters, sea urchins, and abalone, because they offer the greatest caloric reward. In soft-bottom habitats prey are often smaller and more difficult to find and they end up eating a variety of burrowing invertebrates such as pismo clams, Tivela stultorum. Enhydra lutris most often forages in habitats where water is less than 40 meters deep, though juvenile males may forage somewhat deeper. They always return to the surface for feeding and will often also bring a rock to the surface to use to crush the shells of sea urchins, crabs or other shellfish. They will balance the prey on their chest and belly and use their forepaws to hold and manipulate the rock. They may also use a rock in order to retrieve an abalone from the bottom by smashing it open.

Enhydra lutris has three different types of teeth each necessary to eat such a variety of prey. They use their spade-shaped lower incisors for scooping clams or sea urchins from their shells, whereas their flattened molars are used for crushing hard-shelled invertebrates and their round and blunt canines are used to pry open bivalves. Most otters specialize in only one to three prey species, such as kelp crabs, rock crabs, turban snails, red abalone, urchins or mussels. However, when a female has a pup, she may change her foraging habits to focus on easily captured prey, possibly to teach the pup these techniques.

Enhydra lutris uses its spade-shaped lower incisors to scoop clams or sea urchins from their shells. Their molars are flattened and rounded for crushing hard-shelled invertebrates, their favorite prey. The otter's canines are round and blunt; they are used to pry open bivalves. Most sea otters specialize in only one to three prey species, such as kelp crabs, Pugettia sp., rock crabs, Cancer sp., turban snails, Tegula sp., red abalone, Haliotis rufescens, urchins, or mussels. When she pups, a female sea otter often changes her foraging habits to forcus on easily captured prey, possibly to teach her youngster these techniques.

Seasonal Behavior

January - December

Reproduction:

Male Enhydra lutris reaches sexual maturity at five to six years of age with most females mature by four years. While no set breeding season is observed, peaks occur from May to June in northern populations and January to March in southern populations.

These otters are polygynous, meaning that the male will have multiple female mates. Males establish aquatic territories that they will defend, usually just by posturing versus fighting, in areas near females and their pups. Courtship is very playful, but can also be aggressive since males often bite the females on the neck or nose. Thus sexually mature females may end up with bloody noses during the breeding season and older females may have distinguishing scars.

Gestation lasts about 9-10 months and females give birth throughout the year. In southern populations, most pups are born between December and February, while in the North, most are born from May to June.

Females nurse their pups for about 6 months, but sometimes as long as a year. While nursing, females continue foraging and by the time the pups are six weeks old they may begin to forage as well. Once pups are weaned, they are abandoned, but by this time they have learned how to hunt, dive and groom effectively from their mothers.

References

• Langstroth, L. and L. Langstroth. 2000. A Living Bay: The Underwater World of Monterey Bay. University of California Press, Berkeley and Los Angeles, CA. 287 p.
• Reeves, R.R., B.S. Stewart, P.J. Clapham, and J.A. Powell. 2002. National Audubon Society Guide to Marine Mammals of the World. A.A. Knopf, New York, NY. 527 p.
• WWW
  Monterey Bay Aquarium. Online Field Guide, 2008.
  http://www.mbayaq.org/efc/living_species/
  Accessed [04/27/06]
  Accessed 01/30/2009 for Pelagic Cormorant
  Accessed 8/19/09 for Bryozoan
  Accessed 7/31/09 for Spiny brittle star
  Accessed 3/31/09 for Sunflower star
  Accessed 8/9/09 for red octopus
  Accessed 8/19/09 for Decorator crab
  Accessed 7/31/09 for warty sea cucumber
  

Related Information