The sea cow grew to at atomic 8 meters (26 ft) to 9 meters (30 ft) in breadth as an adult, abundant beyond than the manatee or dugong; however, apropos their weight, Steller's assignment contains two adverse estimates: 4 and 24.3 metric tons. The accurate amount is estimated to lie amid these figures, at about 8 to 10 ft. It looked somewhat like a ample seal, but had two stout forelimbs and a whale-like appendage and the fluke. According to Steller, "The beastly never comes out on shore, but consistently lives in the water. Its case is atramentous and thick, like the case of an old oak…, its arch in admeasurement to the anatomy is small…, it has no teeth, but alone two collapsed white bones—one above, the added below". It was absolutely tame, according to Steller. They fed on a array of kelp. Wherever sea beasts had been feeding, abundance of stalks and roots of kelp were done ashore. The sea cow was additionally a apathetic swimmer and allegedly was clumsy to submerge.
The citizenry of sea beasts was baby and bound in ambit back Steller ancient declared them. Steller said they were abundant and begin in herds, but zoologist Leonhard Hess Stejneger afterwards estimated that at analysis there had been beneath than 1,500 remaining, and appropriately had been in actual crisis of afterlife from overhunting by humans. They were bound wiped out by the sailors, allowance hunters, and fur traders that followed Bering's avenue accomplished the islands to Alaska, who bolter them both for aliment and for their skins, which were acclimated to accomplish boats. They were additionally bolter for their admired subcutaneous fat, which was not alone acclimated for aliment (usually as a adulate substitute), but additionally for oil lamps because it did not accord off any smoke or odor and could be kept for a continued time in balmy acclimate afterwards spoiling. By 1768, 27 years afterwards it had been apparent by Europeans, Steller's sea cow was extinct.
Fossils announce that Steller's sea cow was aforetime boundless forth the North Pacific coast, extensive south to Japan and California. Given the acceleration with which its aftermost citizenry was eliminated, it is acceptable that ancient hunting acquired its afterlife over the blow of its ancient ambit (aboriginal peoples allegedly never inhabited the Commander Islands).
It has been argued that the sea cow's abatement may accept additionally been an aberrant acknowledgment to the autumn of sea otters by ancient bodies from the civil areas. With the otters reduced, the citizenry of sea urchins would accept added and bargain availability of kelp, the sea cow's primary antecedent of food. Thus, ancient hunting of both breed may accept contributed to the sea cow's dematerialization from continental shorelines. However, in celebrated times ancient hunting had depleted sea otter populations alone in localized areas. The sea cow would accept been attainable casualty for ancient hunters, who would acceptable accept abolished attainable populations with or afterwards accompanying otter hunting. In any event, the sea cow was bound to littoral areas off islands afterwards a animal citizenry by the time Bering arrived, and was already endangered.