and that sea otters may die if their fur is contami- 

 nated by oil, the current population size and dis- 

 tribution is marginal to insure survival. 



PRIORITY INDEX 



Not assigned. 



DESCRIPTION 



Although the smallest of marine mammals, 

 the sea otter is the largest member of the weasel 

 family. Adult otters in California weigh from 20 

 to 39 kg and are from 1 to 1.6 m long. The dense, 

 dark-browTi fur may become grizzled with age, 

 especially in older males, and the forelimbs are 

 modified for feeding, while the flipper-like hind 

 limbs are used in swimming (Merriam 1904, 

 Kenyon 1969). The skull is flattened dorsally, 

 with large nasal openings; two rear upper cheek 

 teeth are wider than long; there are three upper 

 premolars and two lower incisors on each side of 

 the jaw (Hall and Kelson 1959). 



RANGE 



Originally found from Morro Hermoso, Baja 

 California, north along the Pacific Coast to Cali- 

 fornia, Oregon, and Washington, the sea otter is 

 currently restricted to coastal waters of central 

 California. Established populations now occur 

 from Ano Nuevo Island in the north to Avila 

 Beach to the south (Wild and Ames 1974). Occa- 

 sional individuals are seen in California as far 

 north as Humboldt County and as far south as 

 Los Angeles County. 



RANGE MAP 



The extent of coastline supporting established 

 populations of the southern sea otter is shown 

 by shading on the accompanying map (Wild and 

 Ames 1974, R. J. Jameson, pers. observ.). 



STATES/COUNTIES 



California 



HABITAT 



Santa Cruz, Monterey, San Luis 

 Obispo 



Otter habitat is the neritic zone within 3 miles 

 of shore; the animals are usually found within 

 one-half mile of shore and occasionally on shore. 



Associated with a wide variety of sublittoral 

 communities, the presence of an adequate food 

 supply is an important factor in determining the 

 presence of sea otters (Woodhouse et al. 1977). 

 Although found over sandy substrates, sea otter 

 population centers seem to be associated with 

 hard substrates and stands of kelp [Macrocystis 

 pyrifera and Nereocystis lutkeana). Water depth 

 ranges from to 36 m, in California, sea otters 

 are usually found in depths of less than 25 m. 

 Shelter from storm waves seems to be a require- 

 ment, either in the form of kelp beds or sheltered 

 coves (Kenyon 1969). 



FOOD AND FORAGING BEHAVIOR 



Food supply represents a critical environ- 

 mental factor for sea otters. A sea otter consumes 

 about 20% to 25% of its body weight in food 

 each day (Kenyon 1969), and a meal passes 

 through the digestive tract in about 2.8 hr (Stull- 

 ken and Kirkpatrick 1955). This large volume of 

 food is apparently needed to maintain body tem- 

 perature in cold waters (Morrison et al. 1974). To 

 meet these requirements, Loughlin (1977) found 

 that radio-tagged otters spent 34% of their total 

 time (or 73% of their active time) in foraging. Sea 

 otters are active both day and night, and 45% of 

 their foraging is nocturnal (Loughlin 1977,Shimek 

 and Monk 1977). Feeding is usually in water 1 to 

 25 m deep. Occasionally, individuals will leave the 

 water at low tide to forage for mussels {Mytilus 

 calif ornianus) , but they return to the water to eat 

 them (R. J. Jameson, unpubl.). Foraging dives 

 range from 10 to 120 sec, but are usually less than 

 60 sec long. Depth of water and availability and 

 type of prey seem to be important factors in de- 

 termining the length of these foraging dives. Food 

 is usually gathered from the bottom, but Califor- 

 nia sea otters spend considerable time foraging in 

 the kelp canopy where snails {Tegula spp) and 

 kelp crabs {Pugettia producta) are abundant. A 

 stone 'tool' may be used to break hard-shelled 

 molluscs, such as abalone, from the bottom 

 (Houk and Geibel 1974) and at the surface, this 

 tool may be used as an anvil to break mollusc 

 shells (Hall and Schaller 1964). Woodhouse et al. 

 (1977) conclude that the type of food eaten cor- 

 responds to availability more than to preference, 

 although foraging energetics certainly favors the 

 collecting of food items with high caloric rewards. 

 Foods commonly taken by sea otters in Call- 



