Northern elephant seal

Natural history

An elephant seal dives deep and long to find food and avoid white sharks, a major predator. These master divers usually descend to about 1,700 feet (518 m). But researchers have recorded much deeper dive depths of 5,015 feet (1,529 m). Only sperm whales dive deeper and longer.

An elephant seal seldom stays at the surface for more than a few minutes. They typically dive for more than 80 minutes at a time, although much longer dive times have been recorded. One researcher who monitored a female elephant seal for 34 days recorded that the seal dove almost continuously, resting at the surface for only about three minutes between dives. Some experts believe that an elephant seal naps while gliding down to the depths.

Along the California coast, the elephant seal breeds on the beaches of Año Nuevo, Piedras Blancas and the Channel Islands.

Conservation

Hundreds of thousands of northern elephant seals lived in the Pacific Ocean before hunters slaughtered them for their blubber, which was used to make lamp oil. By the late 1800s, the only remaining colony—fewer than 100 seals—lived on Mexico’s Guadalupe Island. To save them, the Mexican government gave protected status to northern elephant seals in 1922. A few years later, when elephant seals began appearing in southern California waters, the United States gave the seals the same protection. As a result, the population of northern elephant seals is about 160,000 today. The elephant seal’s mighty comeback is an example of the importance of protective status and marine sanctuaries in ocean conservation.

Migration and breeding

The northern elephant seal is the only mammal known to make two migrations each year. After the breeding season (from December through March on Californian and Mexican beaches), it migrates to feeding grounds in the northern Pacific Ocean. The seal returns to warmer waters to molt, then migrates back to feeding areas until the next breeding season.

The northern elephant seal returns to the same beaches year after year during the breeding season. The male arrives at the rookeries first, ready to battle other males to decide who will be dominant and have land rights for a harem of females, which arrive later. Fighting is fierce, but the male is protected by a pink “chest shield” formed from keratinized skin.

Pups

An elephant seal pup nurses for about four weeks and gains about 10 pounds (4.5 kg) a day.

About 24 days into the weaning period, the female mates and then abruptly goes to sea. She leaves behind her pup, which must learn to swim and forage on its own before it too leaves the beach at about two to three months of age.

Blubber loss

Breeding, defending territory, birthing and caring for pups are all so intense that the elephant seal fasts while on the rookeries, using stored blubber for nutrition and energy. When males leave the breeding beaches and return to the water, they may have lost up to half their body mass.

Cool facts

• The elephant seal, like other mammals, must replace old skin and hair. Most mammals shed hair year-round, but the elephant seal does it all at once. Once each year, the seal comes ashore and sheds the first layer of skin and fur, which come off in sheets as new skin and fur replace the old.