Steller’s Sea Cow

Steller’s Sea Cow, long-extinct, herbivorous, aquatic mammal related to the manatee and dugong. The only record of these animals is from Georg Wilhelm Steller, a German physician and naturalist. He discovered the enormous sea cow in 1741 when he and a Russian exploring party were shipwrecked on the Commander Islands in the Bering Sea. By the time Steller discovered these sea cows, their range had become limited to waters near these islands. In prehistoric times, the sea cow’s habitat ranged from the rim of the North Pacific near Japan to Baja California in Mexico.

These massive, placid creatures inhabited shallow, sandy areas along the shore. Steller wrote that they particularly liked “the mouths of the gullies and brooks, the rushing fresh water of which always attracts them in herds.” Showing no fear of humans, the sea cows allowed themselves to be touched from the shore.

Steller’s sea cows reached lengths of at least 7.4 m (24 ft) and may have weighed up to 10 tons. A Steller’s sea cow skeleton in the Leningrad Zoological Museum measures just over 7 m (23 ft). Their heads were small relative to their rotund bodies, and their tiny eyes, Steller wrote, were no larger than sheep’s eyes. Their short forelimbs ended in bristled, hooflike flippers. Their skin was dark brown, rough as tree bark, and sometimes streaked or spotted with white. The skin was also remarkably tough and elastic; a scientist in Hamburg, Germany, rehydrated a piece of preserved sea cow hide and remarked on its surprising resemblance to the thick rubber of car tires. This durable skin protected the giant mammal as it swam near rocks and sharp-edged ice floes.

Steller’s sea cows fed exclusively on kelp growing around the Commander Islands. Lacking teeth, they ground the seaweed between two bony chewing plates. To satisfy their large appetites, they spent most of their time feeding with their heads down and their backs exposed above the water surface.

Steller guessed that most calves were born in the autumn, although he believed that some reproduction occurred year-round. He observed that mating took place in the spring. He also noted that these gentle animals protected their young, always putting them in the middle when swimming in groups. Steller further noted that when a sea cow was harpooned, others would immediately gather around it, and some would even try to overturn the hunter’s dinghy. Sea cows would also lie on their side next to the wounded animal and would also try to pull the harpoon out of the body—sometimes succeeding.

At the time that Steller discovered this species, there were an estimated 1500 to 2000 sea cows. Steller and the rest of his exploring party were eventually rescued and returned to Russia laden with valuable otter, seal, and Arctic fox furs. Word spread to hunters of the fortune to be made in fur trade from the Commander Islands. From 1743 to 1763 hundreds of hunters arrived in the Bering Sea. They found this slow-moving sea cow an easy target for meat, blubber, and hide. By 1768, 27 years after it was discovered, the Steller’s sea cow had become extinct.

Scientific classification: The Steller’s sea cow belonged to the family Trichechidae of the order Sirenia.