Steller's sea cow

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Steller's sea cow[1]
Drawing thought to be the only remaining illustration of a dead female examined by Steller, 1743. Many later depictions were based on it.
Conservation status

Extinct  (1768)  (IUCN 3.1)[2]
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Sirenia
Family: Dugongidae
Subfamily: †Hydrodamalinae
Palmer, 1895
Genus: †Hydrodamalis
Retzius, 1794
Species: †H. gigas
Binomial name
Hydrodamalis gigas
(Zimmermann, 1780)

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".[3] 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,[4] 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.

Description

Skeleton in Finland

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.[5] The true value is estimated to lie between these figures, at around 8 to 10 t.[6] It looked somewhat like a large seal, but had two stout forelimbs and a whale-like fluke.

According to Steller, it "is not the sea cow of Aristotle, for it never comes upon dry land to feed" but it can use its forelimbs for a number of tasks: swimming, walking on the shallows of the shore, supporting himself on the rocks, digging for algae and seagrasses, fighting, and embracing each others.[7]

"It is covered with a thick hide, more like unto the bark of an ancient oak than unto the skin of an animal; the manatee’s hide is black, mangy, wrinkled, rough, hard, and tough; it is void of hairs, and almost impervious to an ax or to the point of a hook."[7]

Its head is small and short compared to the huge body. The upper lip is so large, so broad, and extends so far beyond the mandible, that the mouth appears to be located underneath the skull. The mouth is rather small, toothless, and equipped with double lips, both above and below. When it closes its mouth, the space between the lips are filled up with a dense array of very thick white bristles, 1.5 in (38 mm) long. These bristles take the place of teeth and are used to pull out seaweed and hold food. Mastication is performed by two white bones or solid tooth masses.[7]

Behaviour

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.[8]

Habitat

1988 restoration from the Soviet Union

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.[9] There is evidence that sea cows also inhabited the Near Islands during historic times.[10] Oral tradition on Attu stated that sea cows were still hunted there after their extinction on the Commander Islands.[11]

Skull

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).[12]

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.

Hydrodamalis gigas skeleton with incorrectly restored hands, Muséum national d'histoire naturelle, Paris

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.[12] However, in historic times aboriginal hunting had depleted sea otter populations only in localized areas.[12] 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.[13] It has been demonstrated [14] that the extinction of the sea cow could have been effected solely by the hunting of the sea cow for meat by fur-trading mariners of the time, and no other factors needed to have contributed.

See also

References

  1. ↑ 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. 
  2. ↑ Domning, D., Anderson, P. K. & Turvey, S. (2008). Hydrodamalis gigas. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 29 December 2008.
  3. ↑ 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. 
  4. ↑ "Steller's SeaCow". Sirenian.org. Retrieved 18 May 2011. 
  5. ↑ Sally M. Walker (1999). Manatees. Lerner Publications. 
  6. ↑ 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. 
  7. ↑ 7.0 7.1 7.2 ""De Bestiis Marinis, or, The Beasts of the Sea (1751)" by Georg Wilhelm Steller, Walter Miller (Translator) et al." (in English). University of Nebraska Lincoln. Retrieved January 2014.  (PDF)
  8. ↑ 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. 
  9. ↑ Self-Sullivan, Caryn (2007-02-25). "Evolution of the Sirenia". Sirenian International. Retrieved 2007-04-19. 
  10. ↑ 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
  11. ↑ Lucien McShan Turner (2008) An Aleutian Ethnography, University of Alaska Press
  12. ↑ 12.0 12.1 12.2 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. 
  13. ↑ 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. 
  14. ↑ Turvey ST; Risley CL. (2006) Modelling the extinction of Steller's sea cow. Biology Letters http://www.ncbi.nlm.nih.gov/pubmed/17148336

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