Northern Elephant Seal: Facts, Size, Diving and Habitat

What does a northern elephant seal look like?

Elephant seals are true seals, members of the family Phocidae. Like harbor and gray seals, they have no external ear flaps, short front flippers, and hind flippers that cannot turn forward under the body. On land they move by heaving their body along in waves, an awkward-looking motion that can still be surprisingly quick over short distances. The differences from sea lions are explained in seal vs sea lion.

Adults are brown to gray, often fading to tan before their yearly molt. Pups are born with black fur, which they shed for a silvery coat around the time they are weaned. The eyes are large and dark, adapted for seeing in very dim light, and the long whiskers are sensitive enough to detect the water movements of nearby prey.

Adult males look very different from females. They grow a large, inflatable nose, or proboscis, that hangs over the mouth by about 20 cm (8 in), and a thick, pinkish shield of calloused skin on the neck and chest that protects them during fights. Females keep a normal seal nose and a smooth neck. The reasons for the male’s nose are explored in Why do elephant seals have big noses?

How big are northern elephant seals?

Few mammals show such a large difference between the sexes. Males usually weigh three to four times as much as females, and the largest bulls can be more than five times heavier than a small adult female.

Only its relative, the southern elephant seal of the sub-Antarctic, is bigger. Size comparisons with walruses and other giants are covered in How big is an elephant seal?

Where do northern elephant seals live?

Northern elephant seals live in the eastern and central North Pacific Ocean. They come ashore only to breed and molt, at colonies called rookeries on offshore islands and remote mainland beaches. The main rookeries are in Mexico, on Isla Guadalupe, the San Benito Islands and Isla Cedros off Baja California, and in California, on the Channel Islands, which hold most of the US population, and at Piedras Blancas, Año Nuevo, the Farallon Islands and Point Reyes. A few pups are now born in Oregon and British Columbia.

Away from the beaches, the sexes feed in different places. Males travel north along the edge of the continental shelf to the Gulf of Alaska and the eastern Aleutian Islands, where they often hunt near the seafloor. Females range more widely across the open northeast Pacific, hunting in mid-water far from land.

Because they make two long trips each year, one after breeding and one after molting, adults can travel up to about 21,000 km (13,000 mi) a year, one of the longest migrations of any mammal. See the longest animal migrations for how this compares.

What do elephant seals eat and how deep do they dive?

Northern elephant seals are carnivores that feed mainly on deep-water squid and fish, including lanternfish and Pacific hake. They also eat small sharks, rays, ratfish and hagfish. Males take more seafloor prey, while females hunt mostly in the open water column.

Hunting means diving, almost without a break. At sea, elephant seals dive day and night, typically to about 300–760 m (1,000–2,500 ft) for 20–30 minutes, and spend only two or three minutes at the surface between dives. The deepest dive recorded for the species is about 1,735 m (5,692 ft), and the longest dives last more than an hour. How they manage it, by breathing out before diving and storing oxygen in their blood and muscles, is explained in How long can seals hold their breath?

Elephant seals even sleep while diving. A 2023 study that recorded the brain activity of wild seals found they sleep only about two hours a day at sea, in short naps taken deep underwater, sometimes while slowly spiraling downward.

Breeding season: bulls, harems and beach battles

The breeding season runs from December to March. Bulls arrive first and fight to establish a ranking. They rear up chest to chest, roar threats and slam their heavy necks together, biting at each other’s chest shields. Many contests end with a display alone, when the weaker male backs away.

Pregnant females arrive from mid-December and gather in dense groups, often called harems. Each female gives birth to a single pup within a few days of coming ashore and nurses it for about four weeks on extremely rich milk. In that time a pup roughly triples or quadruples its birth weight, while the mother eats nothing and loses a third or more of her own body weight. Near the end of nursing she mates, usually with the dominant bull of her group, and then leaves for the sea.

Only a small minority of bulls father most of the pups, and many males never mate at all. A top bull may guard dozens of females and stay on the beach for up to three months without eating or drinking, losing up to 36% of his body weight. Weaned pups stay on shore for another 8–12 weeks, living on their fat stores while they learn to swim in the shallows before their first trip to sea.

Molting on the beach

Elephant seals go through what is called a catastrophic molt. Instead of losing hair a little at a time, they shed the outer layer of skin and fur in large patches over about four to five weeks. Because extra blood flows to the skin during this time, they would lose too much heat in cold water, so they stay on land and fast.

Females and young seals molt in spring, and adult males return later, in summer. Molting seals often look ragged and peeling, which is normal and not a sign of illness.

Predators and threats

Great white sharks and orcas are the main natural predators. The great white shark hunts elephant seals off central California, especially near islands with large colonies. On the beaches, pups are sometimes crushed when bulls charge through crowded groups, and strong El Niño storms can wash many pups off the sand.

Human threats today include entanglement in fishing gear and plastic debris, collisions with boats, and disturbance by people on beaches. Warming seas may also be shifting where the seals breed: colonies in Baja California have declined in recent decades while those in California have grown. Scientists are watching for H5N1 bird flu, which in 2023 killed most of that season’s pups in a southern elephant seal colony in Argentina.

Conservation status and recovery

The northern elephant seal is one of the great conservation success stories. In the 1800s it was hunted for oil made from its thick blubber until it was thought to be extinct. In 1892 a small group was found on Isla Guadalupe off Mexico, and the population may have fallen to only a few dozen animals, possibly as few as 20–40. Mexico protected the species in 1922, the United States followed, and the Marine Mammal Protection Act of 1972 strengthened its protection.

Today there are more than 200,000 northern elephant seals, and the IUCN Red List classifies the species as Least Concern with an increasing population. The near-extinction left a lasting mark, however: the species has very little genetic diversity, which could make it more vulnerable to disease or rapid environmental change.

Myths and facts

• Myth: the male’s nose works like an elephant’s trunk. It looks like one, but it cannot grab or lift anything. The proboscis is an enlarged, inflatable nasal chamber that hangs over the mouth and mainly helps the bull make and show off his threat calls.
• Myth: a young elephant seal alone on the beach has been abandoned. In late winter and spring, weaned pups are supposed to be on their own. Their mothers have already returned to sea, and the pups live off their fat for weeks while they learn to swim.
• Myth: elephant seals rest by floating at the surface. At sea they barely surface at all between dives. They take their short naps deep underwater instead, which may help them avoid sharks and orcas near the surface.

Watching elephant seals

As numbers grew, elephant seals spread north to new beaches. They began breeding at Año Nuevo in the early 1960s and at Point Reyes, where the first pup was found in 1976, and they settled on the mainland beach at Piedras Blancas only in the 1990s. That colony is now one of the largest on the mainland, with a public viewing area beside Highway 1.

Visitors can watch the noisy breeding season in winter, the molt in spring and summer, and young seals resting on the sand in autumn. In the United States, it is illegal to harass marine mammals, and NOAA recommends staying at least 50 yards (46 m) away. Keeping that distance protects both the seals and the people watching them.