Steller Sea Lion

About the Species

The Steller (or northern) sea lion is the largest member of the family Otariidae, the “eared seals,” which includes all sea lions and fur seals. Steller sea lions are named for the German surgeon and naturalist Georg Wilhelm Steller. In 1742, he observed and described these large pinnipeds. Steller sea lions' impressive low-frequency vocalizations sound more like a roar when compared to California sea lions which sound more like a bark.

Historically, Steller sea lions were hunted for their meat, fur hides, oil, and various other products. Due to conflicts with fishermen, numbers were further reduced in the early 1900’s when there was a bounty placed on the species. Intentional killing of Steller sea lions has not been permitted since 1972, when they were protected under the Marine Mammal Protection Act and listed under the Endangered Species Act.

Of note, the Eastern population of Steller sea lions was removed from the list of threatened and endangered species in November 2013 as a direct result of the recovery efforts and protections provided by the ESA. The Western population is still listed as endangered. 

NOAA Fisheries reamains dedicated to the conservation of Steller sea lions. Our scientists use a variety of innovative techniques to study and protect these animals. We also work with our partners to ensure that regulations and management plans are in place to reduce entanglement in fishing gear, create safer shipping lanes, and protect habitats.

Status

For management purposes, Steller sea lions inhabiting U.S. waters have been divided into two distinct population segments (DPS):

• The Western DPS includes Steller sea lions born west of Cape Suckling (144° west longitude).
• The Eastern DPS includes Steller sea lions born east of Cape Suckling.

The differentiation is based primarily on genetic and physical differences, but also on differing population trends in the two regions.

The decline in the abundance of Steller sea lions was first observed in Alaska in the late 1970s, and the rate of decline increased dramatically in the late 1980s which prompted NOAA Fisheries to list the species range-wide as threatened in 1990. The two DPSs were first recognized in 1997, with the Eastern DPS retaining its threatened status, while the status of the Western DPS was changed to endangered because of continued declines through the 1990s. 

The Eastern DPS has since recovered due to a more than 30 year period of population increase and was removed from ESA protection (de-listed) in 2013.

The Western DPS in Alaska is increasing slowly overall, but abundance continues to decline sharply in the Western and Central Aleutian Islands. A recovery plan guides actions to recover the Western DPS and a post-delisting monitoring plan guides monitoring for the Eastern DPS to ensure that it continues to thrive.

The reasons for these differing trends of the Eastern and Western DPSs are not clear, but may be related to food availability and the combined effects of commercial fishing, climate change, and contaminants.

View the stock assessment reports for the Steller sea lion

Appearance

Steller sea lions exhibit sexual dimorphism which means that adult males are noticeably larger than females and further distinguished by a thick mane of coarse hair. Adult males may be up to 11 feet long and can weigh up to 2,500 pounds. Females are smaller than males, at 7.5 to 9.5 feet long and weigh up to 800 pounds.

The coats of adult males and females are light blonde to reddish brown and slightly darker on the chest and abdomen. The light coloration is still visible when the body is wet. Like other pinnipeds, their coat of fur "molts,” or sheds, every year.

Both sexes also have long whitish whiskers, or vibrissae, on their muzzle. The flippers and other hairless parts of the skin are black. The fore-flippers are broader and longer than the hind-flippers and are the primary means of locomotion in water. On land, sea lions, unlike "true" seals, can turn their hind flippers forward for walking.

Behavior and Diet

Steller sea lions are opportunistic predators, foraging and feeding primarily at night on a wide variety of fishes (including capelin, cod, herring, Atka mackerel, pollock, rockfish, salmon, and sand lance) and cephalopods (including squid and octopus). Their diet varies depending on the abundance and distribution of prey. Steller sea lions may disperse and range far distances to find prey (particularly adult males during the winter), but are not known to migrate.

Steller sea lions forage near shore and in open waters. They are also capable of traveling long distances in a season and can dive to approximately 1,300 feet in depth. They use land habitat as haul-out sites for periods of rest, molting, and as rookeries for mating and pupping during the breeding season. At sea, they are seen alone or in small groups, but may gather in large "rafts" at the surface near rookeries and haul-outs. They are capable of powerful vocalizations that are accompanied by a vertical head bobbing motion by males.

Where They Live

Steller sea lions prefer the colder temperate to sub-arctic waters of the North Pacific Ocean. Haul-outs and rookeries usually consist of beaches (gravel, rocky or sand), ledges, rocky reefs. In the Bering Sea and Okhotsk Sea, sea lions may also haul out on sea ice. Steller sea lions are distributed mainly around the coasts to the outer continental shelf along the North Pacific Ocean rim from northern Hokkaiddo, Japan through the Kuril Islands and Okhotsk Sea, Aleutian Islands and central Bering Sea, southern coast of Alaska and south to California. The population is divided into the Western and the Eastern DPSs at 144° west longitude (Cape Suckling, Alaska). The Western DPS includes Steller sea lions that reside in the central and western Gulf of Alaska, Aleutian Islands, as well as those that inhabit the coastal waters and breed in Asia (mainly Japan and Russia). The Eastern DPS includes sea lions living in southeast Alaska, British Columbia, California, and Oregon.

Lifespan & Reproduction

Steller sea lions are colonial breeders. Adult males, also known as bulls, establish and defend territories on rookeries to mate with females. Bulls become sexually mature between 3 and 8 years of age, but typically are not large enough to hold territory successfully until 9 or 10 years old. Mature males may go without eating for 1 to 2 months while they are aggressively defending their territory. Females typically reproduce for the first time at 4 to 6 years of age, usually giving birth to a single pup each year.

Adult females, also known as cows, stay with their pups for a few days after birth before beginning a regular routine of alternating foraging trips at sea with nursing their pups on land. Female Steller sea lions use smell and distinct vocalizations to recognize and create strong social bonds with their newborn pups.

At birth, pups are about 3 feet in length and weigh 35 to 50 pounds. Pups have a dark brown to black "lanugo" (a thick coat that’s shed after birth) coat until 4 to 6 months old, when they molt to a lighter brown. By the end of their second year, pups are the same color as adults. Females usually mate again within 2 weeks after giving birth. Males can live to be up to 20 years old, while females can live to be 30.

This extreme sexual dimorphism suggests a highly polygynous mating system, where only a small proportion of the sexually mature males father most of the pups in a given season.

Threats

Changes in Prey Availability

The type of prey, access to the prey, and its distribution can change for a variety of reasons. Regional and local prey can change due to changes in climate and oceanography. In addition, cumulative and annual commercial fishery removals may result in a reduced availability of prey for sea lions.

Predation

The primary predators of Steller sea lions are killer whales.

Vessel Strikes

Inadvertent vessel strikes can injure or kill Steller sea lions.

Entanglement

Entanglement and ingestion of fishing gear and marine debris is known to contribute to Steller sea lion injury and mortality. Steller sea lions can become entangled in fishing gear, either swimming off with the gear attached or becoming anchored. Once entangled, sea lions 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. 

Contaminants

Contaminants enter ocean waters and affect Steller sea from many sources, such as oil and gas development, wastewater discharges, runoff, and other industrial processes. Once in the environment, these substances move up the food chain and accumulate in top predators. These pollutants can harm Steller sea lions’ immune and reproductive systems.

Illegal Feeding

Feeding sea lions can lead to many problems including habituation, aggression, negative impacts to fisheries, entanglement, injury, and death. It is illegal to feed sea lions (PDF, 2 pages).

Scientific Classification

Kingdom	Animalia
Phylum	Chordata
Class	Mammalia
Order	Carnivora
Family	Otariidae
Genus	Eumetopias
Species	jubatus