Steller Sea Lion

The Steller sea lion is the largest of the eared seals (Otariidae), found along the coasts and islands of the North Pacific Rim. It is named after the naturalist Georg Wilhelm Steller who first described it in 1741. Known for its massive size, loud roars, and gregarious haul-out behavior on rocky shores, it plays an important role as an apex marine predator in coastal ecosystems.

North Pacific Ocean, including Alaska, Russia (Kamchatka, Kuril Islands), Canada (British Columbia), and northern Japan

Ranges across the North Pacific Rim from California north through British Columbia, Southeast Alaska, the Aleutian Islands, the Bering Sea, Kamchatka, the Kuril Islands, and northern Japan.

Altitude and depth

Primarily found from the surface to depths of about 400 meters, though most foraging dives occur between 30-250 meters.

Seasonal movements

Breeding season occurs from May to July on traditional rookeries; outside this period, individuals disperse widely to forage, with some seasonal movement toward wintering areas.

Coastal and pelagic marine habitats including rocky shorelines, islands, reefs, and continental shelf waters; breeding and haul-out sites occur on remote rookeries and rocky islets.

Adaptations to its environment

Thick blubber layer and dense fur provide insulation in cold ocean waters, while powerful fore-flippers allow agile swimming and enable them to walk on land, unlike true seals. Their large size and vascularized flippers help with thermoregulation between diving and hauling out on land.

Listed as Near Threatened by IUCN; the western population in Russia and the Aleutians experienced severe declines (over 70%) from the 1970s-1990s and remains a concern, while eastern populations have recovered and grown substantially. Overall listing reflects mixed regional trends despite improved conservation outlook.

Estimated population

Approximately 80,000-100,000 individuals globally, with eastern populations increasing (~4% annually) and western populations stabilizing after historic declines.

Historical threats include commercial harvesting, incidental bycatch in fisheries, and competition with commercial fisheries for prey. Climate change affecting prey distribution, pollution, and killer whale predation are ongoing concerns, particularly for the western stock.

Diseases and parasites

Known to be affected by leptospirosis, various parasites including nematodes and cestodes, and occasionally harmful algal bloom toxins such as domoic acid.

Protected under the U.S. Marine Mammal Protection Act and Endangered Species Act (western population listed as endangered until 2013), with critical habitat designations, fishery restrictions near rookeries, and international monitoring programs across Russia, Canada, and the U.S.

Recommended actions

Continued monitoring of western stock recovery, mitigation of fishery interactions and bycatch, protection of key rookery and haul-out sites, and research into causes of regional population disparities.

Steller sea lions have a robust, thick-necked body with a blunt muzzle and light tan to reddish-brown fur that appears almost golden when dry. Males develop a noticeable mane of coarser fur around the neck and shoulders, giving them a lion-like appearance.

Size

Males reach 2.8-3.25 meters in length; females are smaller at 2.1-2.9 meters.

Weight

Adult males weigh 450-1,120 kg, while females typically weigh 160-350 kg.

Distinctive features

They are distinguished from California sea lions by their much larger size, lighter coloration, and broader, more massive head and muzzle shape. Their vocalizations are also deeper and more guttural compared to related otariid species.

Differences between males and females

Pronounced sexual dimorphism exists, with males up to three times heavier than females and possessing a thick mane and more massive skull and neck region.

Highly social, forming large aggregations at rookeries and haul-out sites, with dominant males establishing and defending territories during the breeding season. Outside breeding season, they may form loose non-territorial groups of mixed sex and age.

When it is active

Primarily diurnal with activity peaks during daylight hours for foraging, though they can also feed at night depending on prey availability.

Diet

Opportunistic carnivores feeding mainly on fish such as walleye pollock, herring, salmon, and cod, as well as cephalopods like squid and octopus. Diet composition varies regionally and seasonally based on prey abundance.

How it feeds and hunts

They forage by diving and pursuing prey underwater, often hunting alone or in small groups, using speed and agility to catch fish and cephalopods near the seafloor or in midwater.

Communication

Communication includes loud roars, growls, and barks especially among territorial males, along with visual displays and scent cues for individual and mother-pup recognition.

Interactions with other species

Natural predators include killer whales and occasionally large sharks; they compete with commercial fisheries and other pinnipeds for shared fish resources. They may also share haul-out sites with other pinniped species such as harbor seals.

Role in its ecosystem

As an apex marine predator, the Steller sea lion helps regulate fish and cephalopod populations and serves as an indicator species for the health of North Pacific marine ecosystems.

Breeding occurs from late May to July, with males establishing territories on rookeries and mating with multiple females (polygynous system). Gestation lasts about 11-12 months including a period of delayed implantation, and females typically give birth to a single pup.

Raising the young

Females nurse and care for pups intensively for the first few weeks, alternating between nursing bouts on land and short foraging trips at sea, with weaning occurring gradually over 1-3 years.

Maturity and lifespan

Females typically reach sexual maturity around 3-6 years and males around 8-10 years (though effective breeding often occurs later); lifespan in the wild is roughly 20 years for females and slightly less for males.

Classification

Mammalia > Carnivora > Otariidae > Eumetopias > Eumetopias jubatus

Subspecies

Two subspecies recognized: Eumetopias jubatus jubatus (western population, from central Alaska through Russia to Japan) and Eumetopias jubatus monteriensis (eastern population, from Southeast Alaska to California).

Scientific synonyms

Phoca jubata (original Steller 1771 description)

Recent studies

Recent research has focused on using satellite tagging and genetic analysis to understand the causes of the western population decline, including nutritional stress hypotheses linked to fisheries and ecosystem shifts.

Genome and DNA

The Steller sea lion has a diploid chromosome number of 2n=36; genetic studies have identified distinct population structuring between eastern and western stocks.

Compared with similar species

Compared to the California sea lion, the Steller sea lion is considerably larger, lighter in color, and less vocal in a 'barking' sense, instead producing deeper roars; it is also less agile on land due to its bulkier build.

Steller sea lions are the largest otariid species in the world, with males rivaling small cars in weight. They can dive to depths of over 400 meters and hold their breath for many minutes while foraging.

Where and how to see it

Best observed at established rookeries and haul-out sites in Alaska (such as the Aleutian Islands or Kenai Fjords) and British Columbia during the breeding season from May to July, when large numbers gather on rocky shores.

Risks to humans

Generally low risk to humans, though large males can become aggressive if approached too closely, especially during breeding season; boats and swimmers should maintain a safe distance.

Human uses

Historically hunted for meat, oil, and hides by indigenous peoples and later commercial harvesters; today they are primarily valued for ecotourism and scientific research rather than direct exploitation.

Myths and legends

Indigenous peoples of the North Pacific, including Aleut and other coastal cultures, have long regarded sea lions as important cultural and subsistence resources, featuring them in traditional stories and art.