Northern Elephant Seal

About the Species

The northern elephant seal is the largest of the “true” seal in the Northern Hemisphere. Adult males use their large, inflatable noses during the winter breeding season to resonate sound when vocally threatening each other. The largest colonies of northern elephant seals are found off southern California in the Channel Islands. They have one of the longest migrations of any mammal, some have been recorded traveling over 13,000 miles roundtrip.

Northern elephant seals were once thought to be extinct due to commercial sealing in the 1800s. Populations of northern elephant seals in the U.S. and Mexico were all originally derived from a few hundred individuals surviving in Mexico. Its population began to steadily increase in the early 1900s.

Northern elephant seals, like all marine mammals, are protected by the Marine Mammal Protection Act. 

Status

Though a complete population count of elephant seals is not possible because all age classes are not ashore at the same time, the most recent stock assessment reports with population estimates are available.

Appearance

Northern elephant seal pups are black until they are weaned at about 6 weeks old and they molt and turn light silver. Adults are dark brown or gray.

When males reach puberty at about 7 years old, they develop a large inflatable nose, or "proboscis." The proboscis overhangs their lower lip by about 8 inches. They also develop a robust, thick neck that is heavily creased and lighter in color than their dark bodies. Conversely, females maintain their smaller noses and smooth necks.

Fully grown males can reach lengths of over 13 feet and can weigh nearly 4,400 pounds. Females are significantly smaller than males, but are also quite large growing to about 10 feet long and weighing up to 1,300 pounds.

Behavior and Diet

Northern elephant seals have a diet of mostly squid and fishes, but also rays and sharks.

Northern elephant seals spend much of the year, generally about 9 months, in the ocean. They are usually underwater, diving to depths of about 1,000 to 2,500 feet for 20 to 30 minute intervals with only short breaks at the surface. They are rarely seen out at sea for this reason. While on land, they prefer sandy beaches.

They fast during mating season and can lose up to 36 percent of their body weight during this time. When molting occurs, they shed their short, dense fur along with large patches of old skin. Molting takes 4 to 5 weeks to complete.

Where They Live

Northern elephant seals are found in the eastern and central North Pacific Ocean. Though they range as far north as Alaska and as far south as Mexico, they typically breed in the Channel Islands of California or Baja California in Mexico. Northern elephant seals breed and give birth in California and Baja California, primarily on offshore islands from December to March. Males feed near the eastern Aleutian Islands and in the Gulf of Alaska, and females feed further south, in the offshore waters of Washington and Oregon. Adults return to land between March and August to molt, with males returning later than females. Adults return to their feeding areas again between the spring/summer molt and the winter breeding season.

Lifespan & Reproduction

Pups are born in early winter from December to January. Breeding occurs from December to March, and gestation lasts around 11 months. Northern elephant seals are "polygamous”- males establish dominance over large groups of females during the breeding season.

There is a notable difference in lifespan between males and females. Females generally live for about 19 years, while males only live for about 13 years.

These animals are polygynous breeders with a social hierarchy. Males form harems usually when they are 9 to 10 years of age, battling for status. Adult males use their large, inflatable noses during the winter breeding season to resonate sound when vocally threatening each other.

Females come ashore and within a few days give birth to a pup conceived in the previous breeding season. The pups are weaned for about a month and just before her pup leaves she breeds again and then returns to sea.

Threats

Entanglement in Fishing Gear

Northern elephant seals can become entangled in fishing gear, either swimming off with the gear attached or becoming anchored. Once entangled, seals may drag and swim with attached gear for long distances, ultimately resulting in fatigue, compromised feeding ability, or severe injury, which may lead to reduced reproductive success and death.

Vessel Strikes

Inadvertent vessel strikes can injure or kill seals. The projected increase in ship traffic arising from the opening of trans-polar shipping routes (as arctic sea ice continues to decline) will increase the risk of vessel strikes, and also increase ambient noise and pollution.

Scientific Classification

Kingdom	Animalia
Phylum	Chordata
Class	Mammalia
Order	Carnivora
Family	Phocidae
Genus	Mirounga
Species	angustirostris