Steller or northern sea lions are sometimes confused with California sea lions, but are much larger and lighter in color. Males may grow to 11 feet (3.25 m) in length and weigh almost 2,500 pounds (1120 kg). Females are much smaller and may grow to nine feet (2.9 m) in length and weigh 1,000 pounds (350 kg). 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 sagittal crest (the bump on the top of their heads) as is seen in adult male California sea lions. Adult male Stellers have a bulky build and a very thick neck with longer fur that resembles a lion's mane, hence the name "sea lion."
Stellers are found throughout the North Pacific Rim from Japan to central California. Unlike California sea lions, Stellers tend to remain off shore or haul out in unpopulated areas. Breeding occurs along the North Pacific Rim from Año Nuevo Island in central California to the Kuril Islands North of Japan, with the greatest concentration of rookeries (breeding grounds) in the Gulf of Alaska and Aleutian Islands.
Pups are born on offshore islands from mid-May to mid-July and weigh 35-50 pounds (16-23 kg). Mothers stay with pups for one to two weeks before hunting at sea. Then they spend roughly equal amounts of time hunting and nursing pups on land. Pups usually nurse for a year, but some continue to nurse for up to three years. Mating occurs 10-14 days after the pups are born. Dominant mature males maintain territories for one to two months and mate with many females. During the breeding season, males do not eat.
Steller sea lions eat a variety of fishes, invertebrates, and occasionally other pinnipeds. Known predators are killer whales (orcas) and white sharks.
The current population of Steller sea lions is about 40,000, with about 500 living in California. However, there is great concern about this population, which has dropped by 80% in the last 30 years. In 1997, the western stock in Alaska was listed as endangered and the eastern stock of the Continental United States and Canada was listed as threatened. Reasons for this decline are not known. However, researchers believe that a decline in the fish they eat is the biggest cause. The decline of fish could be due to increasing commercial fisheries in the Gulf of Alaska. Drowning, entanglement in nets, and gunshot are all possible reasons for the Stellers' decline. Stellers are protected under the Marine Mammal Protection Act, which forbids the killing, harming, or harassing of any marine mammal, as well as the Endangered Species Act. With this federal protection, there is hope for the recovery of the Steller sea lion population.
At The Marine Mammal Center
The Marine Mammal Center has not rescued many Steller sea lions because they are threatened and haul out in remote areas. From 1975 to 2009, we have rescued only 30 Steller sea lions. Most of these were orphaned pups. Artemis was a Steller sea lion that was rescued as an abandoned pup from Año Nuevo Island. After almost a year of care, she was released and tracked with a satellite tag. Seven years later, she was seen with a pup of her own! Through our extensive experience in surgical techniques, our veterinarians are also called upon to do field anesthesia for wild Steller sea lions in Alaska. As a threatened species, our work with each animal can directly contribute to the knowledge of their population.
NOAA’s Fisheries Service says more action is needed to help the western Steller sea lion recover. Changes are needed to the areas where commercial fishermen may fish for groundfish off Alaska’s Aleutian Islands to further promote the recovery of the western population of Steller sea lions, and to be in compliance with the Endangered Species Act.