Elephant seals, like all true seals (phocids), lack external ear flaps and crawl on land with rhythmic belly flops. In contrast, eared seals (otariidae), like sea lions, have visible ears and hind flippers they can turn underneath their bodies for "walking." Elephant seals' enormous size and the males' inflated proboscis—resembling a shortened elephant trunk—give these seals their common name.
To find their food and avoid white sharks, a major predator, elephant seals dive deep—usually to about 1,700 feet (519 m)—but researchers have recorded dive depths of 5,015 feet (1,540 m). Elephant seals dive for up to 30 minutes at a time, month after month. They seldom stay at the surface for more than a few minutes. One researcher recorded a female elephant seal for 34 days—the seal dove almost continuously, resting at the surface for only about three minutes between dives. Only sperm whales are better divers. Some experts believe that elephant seals nap while gliding downward to the depths.
Along the California coast, elephant seals breed on the beaches of the Santa Barbara Islands, Año Nuevo and Piedras Blancas.
Hundred of thousands of northern elephant seals lived in the Pacific Ocean before hunters slaughtered them for their blubber, which was rendered into 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—an example of the importance of protective status and marine sanctuaries in the conservation of our oceans.
Elephant seals, like other mammals, must replace old skin and hair. Most animals shed hairs year-round, but elephant seals do it all at once. Once each year, the animals come ashore and shed the first layer of skin and their fur. The skin and fur come off in sheets as new skin and fur replace the old.
Northern elephant seals are the only mammals known to make two migrations each year. After the breeding season (from December through March on Californian and Mexican beaches), they migrate to feeding grounds in the northern Pacific Ocean. They return to warmer waters to molt, then migrate back to feeding areas until the next breeding season. They travel about 21,000 total miles (33,800 km).
Northern elephant seals return to the same beaches year after year during the breeding season. The males arrive at the rookeries first, ready to battle each other to decide who will be dominant and have land rights for a harem of females, which arrive later. Fighting is fierce, but the males are protected by a pink "chest shield" formed from keratinized skin. Several days after their arrival, the females give birth to their pups, which nurse for about four weeks and gain 10 pounds (4.5 kg) a day.
About 24 days into the weaning period, females mate and then abruptly go to sea. They leave behind their pups, which must learn to swim and forage on their own before they too leave the beaches. Breeding, defending territory, birthing and caring for pups are all so intense that the elephant seals fast while on the rookeries, using stored blubber for nutrition and energy.