Endangered Spotlight: Steller Sea Lion (Eumetopias jubatus)

By Hannah Orlove

Steller Sea Lions . Photo: NOAA

Despite what their name might lead you to believe, Steller Sea Lions have nothing to do with stars. Their name comes from the German naturalist George Wilhelm Steller, who officially classified them during his second trip to Alaska in 1741.

However, they’re stellar in other ways: they are the largest eared seals in the world, even bigger than Northern fur seals and California sea lions.  Males can reach twelve feet long and weight 1500  pounds.  Females are slightly smaller at nine feet and 700 pounds. Both start life at four feet long and 40 to 50 pounds.

Steller sea lions are light tan to reddish brown in color. They have a blunt face and a boxy, bear-like head. Adult males do not have a visible bump on the top of their heads, as is seen in adult male California sea lions.  Stellers have a bulky build and a very thick neck, which resembles a lion's mane, hence the name "sea lion."

Breeding and Mating

Steller males operate on a polygynous system, with seasonal harems of fifteen to thirty females for one male. The males arrive at rookeries on exposed rocks and beaches in mid-May and establish territories with visual and vocal threats. Breeding season lasts through July.

Because of the intense territorial disputes and competition, most males don’t start mating until they’re eight or ten years old. They suffer a great deal maintaining and guarding their positions during the breeding season.

Females have roughly a twelve-month gestation period and typically give birth to one pup every other year. They remain with their pups for one to two weeks before hunting at sea.  Pups typically nurse for one year and turn into the common reddish tan of the species at two.

The range of the Steller Sea Lion is the Northern half of the Pacific Rim, from Japan to California, in two-hundred animal herds. While individual herds might travel short distances, they’re considered a non-migratory species.

Prey and Predators

Steller sea lions are opportunistic carnivores, eating anything they can catch from squids to fish to sharks, and can dive up to 100 fathoms – six hundred feet below the ocean surface for up to five minutes.  In turn, they’re hunted by whatever can catch them, which is restricted to large sharks and killer whales, their only natural enemies.

In the 1970’s, the species numbered at 250,000 to 300,000; today, it has dropped down to approximately 50,000.  Researchers believe that over-fishing and pollution are depleting their numbers. Entanglement in nets is another concern.

Steller sea lions are protected under the Marine Mammal Protection Act, which forbids the killing, harming, or harassing of any marine mammal. They are also protected as a threatened species under the Endangered Species Act.

Join us on a whale watching trip to the Farallon Islands to see the stellers!

 

Photo Credits: Mother and pup: Joel Sartore. Rookery: NOAA