TPO 34. STELLER'S SEA COW

The reading passage describes three theories that explain possible causes of the extinction of a marine mammal called Steller's sea cow that lived around Bering Island. And the lecturer points out some problems in these theories refuting them all.

The first theory in the passage states that overhunting by indigenous Siberian people could have been the cause of such an extinction. However, the professor argues that it is unlikely basing on the information about the dimension of both, the sea cow and the Siberian population at that time. He explains that the sea cow was an enormous animal -nine meters long and ten tons of weight- and a few of them could have fed the small villages of Siberian people for months. Therefore, Siberian people could not have caused them to extinct.

The second theory described by the reading suggests that some alterations in the ecosystem could have provoked shortage in kelp, the main source of food of the sea cows, and thus became extinct. The lecturer contends that if such ecological changes really happened other animals in the ecosystem would have also been affected, like a decrease in whale's population, but no fishing ship reported such data. Hence, this theory is flawed.

Finally, in regard to the third theory mentioned by the passage which asserts that the European fur traders who arrived the island after 1741 caused the animal's extinction, the professor points out that when these merchants came to the island, the species was already small. So it must be something else that caused the extinction of Steller's sea cow.