Few sights in the animal world compare to an elephant seal beach in breeding season: multi-tonne bulls rearing up chest-to-chest, roaring through their pendulous noses, while hundreds of females and pups lie packed along the sand. Yet that frantic few months ashore is only a small part of their lives. Elephant seals are, above all, deep-sea animals — long-distance migrants that spend most of the year far offshore, diving almost continuously into the dark.

How big is an elephant seal?

Elephant seals are the largest of all pinnipeds. A big southern elephant seal bull can measure nearly 6 m and weigh about 3.7 tonnes — heavier than many cars and more than seven times the weight of a typical female.

That difference between the sexes is among the most extreme of any mammal. Northern elephant seal males reach up to 4.5 m and 2,300 kg, while females reach about 3.6 m and 750 kg. Southern females weigh 350–900 kg. Size matters to males because only the biggest, most dominant bulls win access to large groups of females.

The “trunk” or proboscis develops as males mature. It acts as a resonating chamber for loud, low threat calls, and it also helps recapture moisture from exhaled breath, which matters during the long fasts on land.

How deep can an elephant seal dive?

Very deep. Elephant seals typically dive to 300–800 m for around 20 minutes, with only a couple of minutes at the surface between dives, and their deepest dives exceed 1,500 m and last up to two hours.

Tracking studies show northern elephant seals spend 80–95% of their time at sea underwater, diving day and night for months at a time. Males average dives of around 350–800 m and females 300–600 m. This makes elephant seals among the deepest-diving air-breathing animals, rivalled mainly by beaked whales and sperm whales.

They manage this with enormous oxygen stores in blood and muscle, a large spleen that releases oxygenated red blood cells during a dive, and the ability to slow their heart rate dramatically. They exhale before diving, letting their lungs collapse at depth, which helps avoid decompression sickness. Recent studies even show elephant seals take short naps during deep dives, spiralling downward while asleep.

What do elephant seals eat?

Mostly squid and fish, especially deep-water species in the mesopelagic “twilight zone” and on the seafloor.

Females tend to forage in the open ocean, following bands of squid and lanternfish that migrate up and down the water column each day. Males more often feed along continental margins and the seafloor, taking larger fish, skates, rays, small sharks and octopuses. Because elephant seals hunt in darkness, they rely heavily on their large eyes and highly sensitive whiskers to detect bioluminescence and water movements made by prey.

Southern elephant seals feed widely across the Southern Ocean; three females tracked from South Georgia travelled up to 2,650 km in a single trip. For other deep-diving predators, see deep sea predators.

How far do elephant seals migrate?

Northern elephant seals make two long migrations a year — one after breeding and one after moulting — and spend about 250–300 days at sea, travelling at least 18,000–21,000 km annually.

That makes them among the longest-migrating mammals. Males head north to forage along the Aleutian Islands and Gulf of Alaska, while females range farther offshore across the northeast Pacific. They return to the same beaches each winter to breed and each spring or summer to moult, when they shed skin and hair in large patches.

How do elephant seals breed?

Elephant seals breed in large, crowded colonies where dominant “alpha” bulls defend groups of females known as harems — typically 20–40 females in southern elephant seals, and sometimes many more.

Bulls arrive first and fight for position, rearing up and slamming their chests and teeth together. Fights leave thick scars on the chest and neck, and only a minority of males ever mate. Females arrive shortly afterwards and give birth to a single pup within days. Pups nurse for about three to four weeks on extremely rich milk and can gain up to 9 kg a day. Females mate again near the end of nursing and then leave; the pup stays behind and fasts for weeks before going to sea on its own.

Both males and females fast throughout the breeding season, living off blubber reserves. A breeding bull may spend months on the beach without eating.

Where can you see elephant seals?

In the Northern Hemisphere, the most accessible colonies are in California, including Año Nuevo State Park, Point Reyes and Piedras Blancas near San Simeon. In the south, South Georgia, Península Valdés in Argentina and Macquarie Island host large colonies.

Winter (December to March) is the time to see fighting bulls and newborn pups in California; spring and summer bring moulting juveniles and females. Always follow posted distances — bulls move surprisingly fast over short distances and can be dangerous.

Are elephant seals endangered?

No. Both species are listed as Least Concern by the IUCN, but the northern elephant seal’s recovery is one of conservation’s great comebacks.

Hunted for their oil-rich blubber in the 1800s, northern elephant seals were reduced to perhaps 100–1,000 animals on Isla Guadalupe off Mexico. Protection by Mexico and the United States allowed them to recover to well over 100,000 animals today, although the population went through a severe genetic bottleneck and has very low genetic diversity. Southern elephant seals were also heavily hunted at South Georgia and other islands until licensed sealing ended in 1964; the total population was estimated at around 650,000 in the mid-1990s.

Modern threats include entanglement, vessel strikes, changes in prey linked to ocean warming, and disease. In 2023 highly pathogenic avian influenza (H5N1) killed large numbers of southern elephant seal pups at Península Valdés in Argentina, a stark reminder that big colonies are vulnerable to sudden outbreaks.