Steller's sea cow
|Steller's sea cow|
|Drawing thought to be the only remaining illustration of a dead female examined by Steller, 1743. Many later depictions were based on it.|
Steller's sea cow (Hydrodamalis gigas) was a large, herbivorous marine mammal. It was the largest member of the order Sirenia, which includes its closest living relative, the dugong (Dugong dugon), and the manatees (Trichechus spp.), and "other than the great whales, likely the largest mammal to exist in historic times". Although the sea cow had formerly been abundant throughout the North Pacific, by 1741, when it was first described by Georg Wilhelm Steller, chief naturalist on an expedition led by explorer Vitus Bering, its range had been limited to a single, isolated population surrounding the uninhabited Commander Islands. 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 to at least 8 to 9 meters (26 to 30 ft) 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 number of sea cows was small and limited in range when Steller first described them; although he had said they were numerous and found in herds, 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. There is evidence that sea cows also inhabited the Near Islands during historic times. Oral tradition on Attu stated that sea cows were still hunted there after their extinction on the Commander Islands.
Fossils indicate that Steller's sea cow was formerly widespread along the North Pacific coast, reaching south to Japan and California in the US. 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).
Population and extinction
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 odour 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.
The artist Etienne de France has compiled a mockumentary, entitled Tales of a Sea Cow, about the purported re-discovery by scientists of a population of Steller's sea cows off Greenland. In fact, the sirenian was never present in the Atlantic Ocean.
- Anderson, P. (1995). "Competition, predation, and the evolution and extinction of Steller's sea cow, Hydrodamalis gigas". Marine Mammal Science 11 (3): 391–394. doi:10.1111/j.1748-7692.1995.tb00294.x.
- World Conservation Monitoring Centre (1996). Hydrodamalis gigas. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 11 May 2006. Database entry includes a brief justification of why this species is listed as extinct
- Shoshani, J. (2005). Wilson, D. E.; Reeder, D. M, eds. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. p. 92. ISBN 978-0-8018-8221-0. OCLC 62265494.
- Domning, D., Anderson, P. K. & Turvey, S. (2008). Hydrodamalis gigas. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 29 December 2008.
- Helene Marsh, Thomas J. O'Shea, John E. Reynolds III (2012). Ecology and Conservation of the Sirenia: Dugongs and Manatees. Conservation Biology 18. Cambridge: Cambridge University Press. p. 19. ISBN 9780521888288.
- "Steller's SeaCow". Sirenian.org. Retrieved 18 May 2011.
- Sally M. Walker (1999). Manatees. Lerner Publications.
- Victor B. Scheffer (November 1972). "The Weight of the Steller Sea Cow". Journal of Mammalogy 53 (4): 912–914. doi:10.2307/1379236. JSTOR 1379236.
- Ellis, Richard (2004). No Turning Back: The Life and Death of Animal Species. New York City: Harper Perennial. p. 113. ISBN 0-06-055804-0.
- Self-Sullivan, Caryn (2007-02-25). "Evolution of the Sirenia". Sirenian International. Retrieved 2007-04-19.
- D. G. Corbett, D. Causey, M. Clemente, P. L. Koch, A. Doroff, C. Lefavre, D. West (2008) "Aleut Hunters, Sea Otters, and Sea Cows", Human Impacts on Ancient Marine Ecosystems, University of California Press
- Lucien McShan Turner (2008) An Aleutian Ethnography, University of Alaska Press
- Anderson, Paul K. (July 1995). "Competition, Predation, and the Evolution and Extinction of Steller's Sea Cow, Hydrodamalis gigas". Marine Mammal Science (Society for Marine Mammalogy) 11 (3): 391–394. doi:10.1111/j.1748-7692.1995.tb00294.x. Retrieved 2008-11-02.
- Ellis, Richard (2004). No Turning Back: The Life and Death of Animal Species. New York City: Harper Perennial. p. 134. ISBN 0-06-055804-0.
|Wikimedia Commons has media related to Hydrodamalis gigas.|
|Wikispecies has information related to: Hydrodamalis gigas|
- Animal Diversity Web
- Steller's sea cow information from the AMIQ Institute
- Georg Steller's De bestiis marinis (1751) (in English)
- Hans Rothauscher's Die Stellersche Seekuh site (in German & English)
- Illustration of a sea cow skeleton and an extract from Steller's description