Northern elephant seal

Mirounga angustirostris

SUBFAMILY

Monachinae

TAXONOMY

Mirounga angustirostris (Gill, 1866), California.

OTHER COMMON NAMES English: Northern sea elephant.

PHYSICAL CHARACTERISTICS

Males: 13.2 ft (4.0 m); 3,750 lb (1,704 kg); Females: 10.6 ft (3.2 m); 1,122 lb (510 kg). Males differ from females in that they have an enlarged proboscis and more highly developed neck with thickened skin than females. The pelage of males is dark gray upper and lighter gray under; females are browner than males and darker. Pups are born with a near black natal coat.

DISTRIBUTION

The breeding range is from northern California to the Baja Peninsula in Mexico. During foraging periods, seals migrate north as far as the Gulf of Alaska and the Aleutian Islands.

HABITAT

Breed and molt on mainland and island beaches of sand and cobble. Forage in deep ocean waters.

BEHAVIOR

Breed in dense colonies where both males and females show strong site fidelity from one season to the next. Males make a distinct vocalization during breeding using the proboscis as a resonating chamber. These calls have dialects for different locations. Animals migrate after breeding to foraging areas and return to the breeding location to molt. After the molt, animals again migrate, making a double roundtrip of over 6,000 miles (10,000 km) each.

FEEDING ECOLOGY AND DIET

Males and females forage in different locations and in different ways. Male go further away from breeding grounds and forage at shallower depths on average than females, and males forage on the edge of the continental shelf, whereas females forage more in open ocean. By two years of age, young seals show similar patterns to adults. Feed mostly on cephalopods (such as squid and octopus) and Pacific whiting fish. The diving pattern of these seals is remarkable. They dive continuously for weeks remaining underwater for 30-120 minutes and going to depths as deep as about 5,000 ft (1,500 m), averaging about 1,650 ft (500 m) for females and 1,090 ft (330 m) for males.

REPRODUCTIVE BIOLOGY

Males are polygynous and in most areas defend harems or large groups of densely packed females. Mating occurs on land and females often mate with males other than the harem master as they leave for sea. Males produce sperm about five years of age but do not become successful breeders until 10 to 12 years. Successful males may only breed for two to four years before they are displaced. Females give birth for the first time from three to seven years of age. They give birth to a single young annually. Lactation is about 27 days and females produce a milk averaging 54% fat.

CONSERVATION STATUS

Not threatened.

SIGNIFICANCE TO HUMANS

These seals are of no particular value to humans other than as an educational experience. Their approachability and close proximity to urban areas allow for controlled visits to learn about their biology and natural history. ♦

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