Photo: Two female Steller sea lions in conversation

"These animals are always yelling at each other," writes photographer Joel Sartore of the Steller sea lions on Alaska's Lowrie Island. Here, two females go nose-to-nose over a disputed bit of territory in a crowded rookery. Alaska's Steller sea lion populations have been in precipitous decline over the last 30 years, and scientists are at a loss to explain the cause.

Photograph by Joel Sartore

Map

Map: Steller sea lion range

Steller Sea Lion Range

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Fast Facts

Type:
Mammal
Diet:
Carnivore
Average life span in the wild:
18 (males); 30 (females)
Size:
7.75 to 9.25 ft (2.4 to 2.8 m)
Weight:
1.2 tons (1.1 metric tons)
Group name:
Raft (in water); colony (on land)
Protection status:
Endangered
Size relative to a 6-ft (2-m) man:
Illustration: Sea lion compared with adult man

Stellers are the largest of all sea lions and they have an appetite to match. These giant pinnipeds hunt fish, squid, octopus and, rarely, smaller seals. They are found off northern Pacific coasts from Japan to California.

Steller sea lion breeding is one of nature's great mass spectacles. When these giants thunder ashore, their favored beaches, called rookeries, disappear under their numbers. Young pups are sometimes crushed by the throng, unheeded by powerful males with only a single purpose in mind. Bulls (males) must establish and hold a beach territory in order to breed. Most do not achieve this until they are nine or ten years of age.

Females begin to reproduce at about five years of age and typically have one pup per year. Sea lion mothers care for their young and recognize them by a keen sense of smell. Females slip into the sea to hunt and return to their young with the day's catch—identifying their own offspring by touch and scent.

These animals are social and also gather at various times throughout the year when mating and breeding are not taking place. Even in crowds, the big bulls are unmistakable—they are three times larger than females.

Most Steller sea lion populations declined markedly in the 1980s and 1990s, even though the animals are protected. Scientists are unsure what factor or combination of factors is responsible for the decline.

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