Wednesday, January 26, 2011

January 26, 2011 : Stellar's Sea Cow (Extinct)

Stellar's Sea Cow

Steller's sea cow (Hydrodamalis gigas) was a large herbivorous marine mammal. In historical times, it was the largest member of the order Sirenia, which includes its closest living relative, the dugong (
Dugong dugon), and the manatees (Trichechus spp.). Formerly abundant throughout the North Pacific, its range was limited to a single, isolated population on the uninhabited Commander Islands by 1741 when it was first described by Georg Wilhelm Steller, chief naturalist on an expedition led by explorer Vitus Bering. Within 27 years of discovery by Europeans, the slow moving and easily captured Steller's sea cow was hunted to extinction.

The sea cow grew at least 8 metres (26 ft) to 9 meters or 30 feet long, much larger than the manatee or dugong. Steller's work contains two contradictory weights: 4 and 24.3 tons. The true value probably lies between these figures, around 8-10 tons. It looked somewhat like a large seal, but had two stout forelimbs and a whale-like tail and the fluke. According to Steller, "The animal never comes out on shore, but always lives in the water. Its skin is black and thick, like the bark of an old oak…, its head in proportion to the body is small…, it has no teeth, but only two flat white bones—one above, the other below". It was completely tame, according to Steller. They fed on a variety of kelp. Wherever sea cows had been feeding, heaps of stalks and roots of kelp were washed ashore. The sea cow was also a slow swimmer and apparently was unable to submerge.

The population of sea cows was small and limited in range when Steller first described them. Steller said they were numerous and found in herds, but zoologist Leonhard Hess Stejneger later estimated that at discovery there had been fewer than 1,500 remaining, and thus had been in immediate danger of extinction from overhunting by humans. They were quickly wiped out by the sailors, seal hunters, and fur traders that followed Bering's route past the islands to Alaska, who hunted them both for food and for their skins, which were used to make boats. They were also hunted for their valuable subcutaneous fat, which was not only used for food (usually as a butter substitute), but also for oil lamps because it did not give off any smoke or odor and could be kept for a long time in warm weather without spoiling. By 1768, 27 years after it had been discovered by Europeans, Steller's sea cow was extinct.

Fossils indicate that Steller's sea cow was formerly widespread along the North Pacific coast, reaching south to Japan and California. Given the rapidity with which its last population was eliminated, it is likely that aboriginal hunting caused its extinction over the rest of its original range (aboriginal peoples apparently never inhabited the Commander Islands).

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