Development of the external morphology, skull and canines of Steller sea lions

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概要

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• To clarify the development of the external morphology, skull and canines of Steller sea lions (Eumetopias jubatus), 79 animals were captured off the coast of Rausu, Rebun Island and Shakotan Peninsula, northern Japan, during January to March between 1994 and 1996. From the measurements of 30 parts of the external morphology, 26 parts of the skull and 9 parts of the canine, changes with age, and relative growth were analyzed. Increases in standard length, condylobasal length and canine length tended to level off at about 5 years in females, while in males, growth of these parts continued for at least 10 years. Comparison of the relative changes in numerous body measurements with increasing standard length indicated that development of the upper half of the body is remarkable in males. Females show remarkable foreflipper growth. Using condylobasal length as the base of measurement, skull width indicated positive allometry in males. In females, these measurements indicated negative allometry, and only the length of the snout showed positive allometry. Relative growth of the external morphology and skull differed in both sexes, but relative growth of the canines was similar. Only canine root length showed positive allometry. Male canines were significantly wider than the female canines. The males had thicker canines, wider skulls and bigger upper bodies than the females. These traits are considered advantageous for males maintaining territories during the breeding season.

• 野生生物保護学会の論文

著者

• 磯野 岳臣

  北海道大学水産学部北洋水産研究施設海洋生態学部門

• Isono Takeomi

  Division Of Marine Ecology Faculty Of Fisheries Hokkaido University

• Isono Takeomi

  Econixe Co. Ltd.

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• Population surveys of Steller sea lions in the Kuril Islands in 1995 and 1996
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• Distribution of the Steller sea lion Eumetopias jubatus during winter in the northern Sea of Japan, along the west coast of Hokkaido, based on aerial and land sighting surveys
• Trace elements in the teeth of Steller sea lions (Eumetopias jubatus) from the North Pacific
• Development of the external morphology, skull and canines of Steller sea lions

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