The Steller’s sea cow, Hydrodamalis gigas (1780)
Phylum : Chordata
Class : Mammalia
Order : Sirenia
Family : Dugongidae
Subfamily : Hydrodamalinae
Genus : Hydrodamalis
Species : H. gigas
- Extinct in 1768
- 9 m long and 10 000 kg
- Northern Pacific
The sea cow grew to at least 8 to 9 meters in length as an adult, much larger than the manatee or dugong; however, concerning their weight, Steller’s work contains two contradictory estimates: 4 and 24.3 metric tons. The true value is estimated to lie between these figures, at around 8 to 10 t.It looked somewhat like a large seal, but had two stout forelimbs and a whale-like 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. It 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 species was quickly wiped out by the sailors, seal hunters, and fur traders who followed Bering’s route past the islands to Alaska, who hunted it both for food and for skins, which were used to make boats. It was also hunted for its 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.
It has been argued that the sea cow’s decline may have also been an indirect response to the harvest of sea otters by aboriginal people from the inland areas. With the otters reduced, the population of sea urchins would have increased and reduced availability of kelp, the sea cow’s primary source of food. Thus, aboriginal hunting of both species may have contributed to the sea cow’s disappearance from continental shorelines. However, in historic times aboriginal hunting had depleted sea otter populations only in localized areas. The sea cow would have been easy prey for aboriginal hunters, who would likely have exterminated accessible populations with or without simultaneous otter hunting. In any event, the sea cow was limited to coastal areas off islands without a human population by the time Bering arrived, and was already endangered.