Mammals
California Sea Lion
Zalophus californianus · also called sea lion
The California sea lion is the pinniped people know best — the sleek brown animal barking on a harbour buoy, balancing a ball in an aquarium show, or porpoising through the surf off a California beach. It is fast, loud, sociable, and unusually clever.
Overview
California sea lions breed on islands off the coast of California and western Mexico and range widely through the eastern North Pacific the rest of the year, with many males travelling as far north as British Columbia and Alaska. They are creatures of the coast and continental shelf, hauling out on rocky shores, beaches, jetties, docks, buoys, and boats in noisy, tightly packed groups.
Eared seal design
California sea lions are otariids — the “eared seals” — and everything about how they move reflects it:
- External ear flaps, small but visible.
- Front-flipper propulsion. They swim by sweeping their long, wing-like fore-flippers, effectively flying underwater, which makes them fast and highly manoeuvrable.
- Mobile hind limbs. They can rotate the hind flippers forward under the body, letting them walk, run, and climb on land — up rocks, onto boats, even up stairs.
They are strong divers, routinely reaching a few hundred metres to feed on schooling fish and squid, and they often hunt cooperatively, herding bait balls with dolphins and seabirds.
Intelligence
California sea lions are a major subject of animal-cognition research. In controlled studies they have shown transitive inference and stimulus equivalence — abstract logical abilities — along with the capacity to learn extensive artificial “languages” of gestures, to keep time to a musical beat, and to retain learned tasks for a decade or more. These abilities, plus their trainability and comfort around people, are why they appear in shows and why the US Navy Marine Mammal Program uses them to recover objects from the seafloor and guard harbours.
Reproduction
Breeding is in summer. Males establish and bark to defend small territories on the rookery beaches, fasting for weeks as they do so; females come and go to feed at sea and give birth to a single pup, which they nurse for six months to a year, recognising it among thousands by voice and smell.
Status
The California sea lion is Least Concern and increasing, having rebounded strongly under legal protection to near the environment’s carrying capacity. The challenges now are mostly ones of abundance and a changing ocean: conflict with fisheries and dams, entanglement in debris, and periodic mass strandings caused by domoic acid from harmful algal blooms and by El Niño food shortages, which hit pups and juveniles hardest.
California Sea Lion: common questions
What is the difference between a sea lion and a seal?
Sea lions are "eared seals" (family Otariidae) and true seals are "earless seals" (Phocidae). Sea lions have small visible ear flaps; true seals have only a hole. Sea lions can rotate their hind flippers under the body to walk and gallop on land and climb rocks and stairs, while true seals cannot and must wriggle on their bellies. Sea lions swim mainly with their large front flippers "flying" through the water; seals scull with their hind flippers. Sea lions are also noisy and social; most true seals are quieter.
How intelligent is a California sea lion?
Among the most tested marine mammals for cognition. A famous long-term study with a sea lion named Rio showed she could perform transitive inference (if A goes with B and B with C, then A goes with C) and grasp equivalence relations — forms of abstract logical reasoning once thought limited to humans and a few primates. Sea lions also learn large sets of hand signals, keep a beat to music, and remember tasks for years, which is why they are common in marine-park shows and have been trained by the US Navy to locate and retrieve equipment and detect swimmers.
Why do California sea lions haul out in huge noisy groups?
They are highly social and gregarious, and safety, warmth, and access to breeding sites all favour crowding together. Males on the breeding rookeries "bark" almost continuously to hold territory, and the raucous honking of a haul-out — on a rocky island, a bait dock, a navigation buoy, or the famous Pier 39 in San Francisco — is one of the most recognisable sounds of the Pacific coast. Outside the breeding season the sexes often separate, with many males travelling far north.
Are California sea lions endangered?
No — the opposite. Protected in the US since 1972, the population has grown steadily and is now near the maximum the ecosystem can support, around a quarter to a third of a million animals. That success brings conflicts — sea lions take fish from nets and lines, haul out on docks and boats, gather at dams and fish ladders to eat migrating salmon and steelhead, and suffer die-offs from toxic algal blooms (domoic acid) and from El Niño food shortages. Some other Zalophus populations fared worse — the Japanese sea lion is extinct and the Galápagos sea lion is Endangered.