Within 27 years of discovery, a species of 30-foot-long manatees went extinct. They may have been around until more recently than you think.

The animal known as Steller's Sea Cow went completely unencountered until 1741 as far as anyone knows, and therefore went unknown to science. It was described by a German naturalist named Georg W. Steller, after whom this particular sea cow got part of its name. Steller went along with Vitus Bering on an expedition of the North Pacific.

This creature made its home in the cold waters near the shores of the Komandor Islands in the Bering Sea (off the easternmost reaches of Russia). It grew to 9–10 meters (over 30 feet) and weighed about 10 metric tons (22,000 pounds). This type of sea cow outgrew present-day manatees by far.

But the sea cow's size made it an easy target. Russian hunters used them for meat on their journeys; the killing was often wasteful. Perhaps Steller's sea cow would still exist in the wild if hunters had taken only what they needed. In 1741, there were about 2,000 in the wild, but by 1768 they had been wiped out entirely. Today, relatives of Steller's Sea Cow may be heading in the same direction. Their numbers are in decline, despite occupying the oceans for millions of years.

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