South American sea lion

Otaria byronia

SUBFAMILY Otariinae

TAXONOMY

Otaria byronia (Blainville, 1820), "Island of Tinian (in error, probably strait of Magellan).

OTHER COMMON NAMES

French: Lion de mer d'Amérique du Sud; German: Mähnenrobbe, Südamerikanischer Seelöwe; Spanish: Lobo común.

PHYSICAL CHARACTERISTICS

Males to 772 lb (350 kg), brownish in color with a rough mane and unusually large neck and head. Females to 331 lb (150 kg), tawny.

DISTRIBUTION

Ocean near the Falkland Islands and eastern coast of South America.

HABITAT

Breeds on sand, cobble, or rock. Found on the Falkland Islands, from southern Brazil to Cape Horn (more than 53 breeding sites in central to southern Patagonia), and north to Peru.

BEHAVIOR

Animals do not make prolonged foraging absences, nor do they migrate. Some colonies are occupied all year. Mating is seasonal. Males display a variety of mating strategies in addition to territoriality. Males vigorously herd females, sometimes injuring them.

FEEDING ECOLOGY AND DIET

The species takes fish, crustaceans, and cephalopods. Males occasionally take young fur seals and penguins. Females make short (three day) foraging trips, typical for sea lions.

REPRODUCTIVE BIOLOGY

Polygynous. The operational sex ratio is 1.2 females per male. As with other otariids, females bear a single pup per year, and have a postpartum estrus.

CONSERVATION STATUS

Not threatened. The species was commercially exploited for oil, and is still killed by fishermen. The population is presently estimated at more than 110,000, which may be 20% of its original numbers. Numbers may be increasing. Populations in the Pacific decline in response to El Niño events.

SIGNIFICANCE TO HUMANS

The species is being taken as bait for king crab pots, and is considered to be a nuisance by other fishermen. ♦

DISTRIBUTION

Ocean from central Mexico to southern California, including Guadalupe Island and the Sea of Cortez. Males migrate north as far as Canada, but females do not.

HABITAT

Breeds on sand or rock from central Mexico to southern California (plus Guadalupe Island and the Sea of Cortez). No mainland breeding sites now exist.

BEHAVIOR

The most successful males defend territories that afford females access to water. Female aggregations move across the beach depending on daily temperatures. This species may perform more aquatic copulations than other otariids.

FEEDING ECOLOGY AND DIET

These are opportunistic feeders, primarily depending on anchovy, whiting, rockfish, cephalopods, mackerel, myctophids, sardines, etc., depending on location, season, and El Niño events. Animals feed at all hours. Feed in groups, and may feed with Steller sea lions where the ranges overlap (San Miguel and Año Nuevo Island, California).

REPRODUCTIVE BIOLOGY

Polygynous. Male biology is typical for otariids. Female California sea lions enter estrus 30 days postpartum, instead of less than 10 days like other otariids. Breed on islands with northern fur seals, but hybrids are not known.

CONSERVATION STATUS

Not threatened. California sea lions were exploited in the nineteenth century, and reached a low of 1,500 in the 1920s. They then increased, displacing the Steller sea lion as the most numerous sea lion in California. Their numbers are now between 211,000 and 241,000 and are growing at 5% per year.

SIGNIFICANCE TO HUMANS

This species is known as the common "circus seal," and has served to introduce generations of humans to the family Otariidae. As a laboratory animal, the species has contributed significantly to what we know about vision, hearing, learning, and cognition in marine mammals. Some consider it a nuisance because it is noisy, increasing, and likely to foul the many human structures (buoys, piers, etc.) it uses as resting sites. ♦

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