Elephant Seal

Elephant Seal, largest and heaviest seal, named for the trunklike extension of the snout in males. Elephant seals are divided into two species. The northern elephant seal lives in a single population near the southwestern coast of the United States and Mexico, occasionally traveling as far north as Alaska. The southern elephant seal inhabits southern and subantarctic oceans, with notable population clusters around the southern Atlantic’s Falkland Islands (Islas Malvinas), the southern Indian Ocean’s Kerguelen Islands, and Macquarie Island, which lies southeast of Tasmania, Australia.

Elephant seals have the greatest size difference between the sexes of any mammal. Adult males, or bulls, can reach 4.8 m (16 ft) in length and 3000 kg (6600 lb) in weight. Females, or cows, grow to 3 m (10 ft) and 900 kg (2000 lb) at the most. Males of the northern species sport a slightly longer trunk and have dark brown coats, while mature southern elephant seals have blue-gray coats.

Bulls are distinguished not only by their size and elongated snout but also by scars lacing their necks and chests. These scars are a legacy of past battles with other males for mating dominance. The females’ significantly smaller body size, in combination with the males’ habitual belligerence, puts cows at risk of injury during breeding.

Like many other mammals, elephant seals replace old skin and hair by molting, or shedding, every year. The seals’ abrupt shedding process, called a catastrophic molt, occurs on land in their breeding grounds. The breeding grounds for northern seals are located on remote islands off the coasts of California and Mexico. Breeding grounds for southern seals are on the Peninsula Valdez, off the coast of South America. The molt is followed by several months of foraging in the ocean, after which the well-nourished seals gather onshore again to breed.

While feeding at sea, elephant seals spend nearly 24 hours a day diving deep to reach their favorite food—bottom fish such as ratfish and spiny dogfish. They also eat squid, eel, small sharks, and seaweed. These seals are considered the champion divers among mammals. By attaching radio packs to the backs of elephant seals and tracking them by satellite, scientists have recorded them diving as deep as 1.6 km (1 mi) and as long as two hours. Researchers are particularly interested in this deep-diving seal’s smooth readjustment to breathing as it surfaces. This readjustment includes reinflating collapsed lungs and other processes that reestablish blood flow. This recovery stage typically causes severe organ damage in humans. By studying the physiology of seals, scientists hope to find clues that will help humans survive stroke, heart attack, and acute injury.

The breeding season takes place from December to January for the northern elephant seal and from September to October for the southern elephant seal. During mating season, a combination of blood pressure and muscular action inflates the male elephant seal’s distinctive trunk to an impressive length of 30 to 45 cm (12 to 18 in). Flaunting this striking sexual display, males arrive at the breeding grounds, or rookery, to stake out territory, challenge and roar at each other, and occasionally fight. Females reach the rookery several weeks later, and each gives birth to a single woolly black pup shortly after coming ashore. Mothers and pups soon learn each other’s individual calls, sometimes joining in vocal duets. This knowledge is critical to the pups’ survival because stormy weather, rough surf, or feuding males can separate mothers from offspring. Using vocalizations, they can find each other again.

Pups nurse on their mothers’ rich milk for nearly a month. During this time the mother seals fast, often losing up to 135 kg (300 lb). Averaging 34 kg (75 lb) at birth, elephant seal pups gain at least 4.5 kg (10 lb) a day. Some bold pups nurse from two or three females. These young gluttons, known as super weaners, grow up to 270 kg (600 lb), which is nearly double the weight of the average weaned pup. Females mate around weaning time and then return to sea for nearly a year of gestation before returning to the rookery.

Elephant seals are natural prey to killer whales and sharks. During the 1800s, the elephant seal was hunted almost to extinction by humans for its blubber, or body fat, which was rendered into oil. This seal was specifically targeted because its large body size yielded plentiful blubber—as much as 658 kg (1450 lb) per animal. By 1892 only 50 to 100 northern elephant seals remained, clustered near Guadalupe Island off of Baja California. All three populations of southern elephant seals were greatly diminished as well. Both species have since been granted protected status by the various governments that have jurisdiction over the waters the seals inhabit. For example, the northern elephant seal is granted complete protection by both the United States and Mexico. As a result of this protection, both species have made a dramatic comeback.

Scientific classification: The elephant seal belongs to the family Phocidae of the suborder Pinnipedia, order Carnivora. The northern elephant seal is classified as Mirounga angustirostris and the southern elephant seal as Mirounga leonina.