GEOGRAPHIC VARIATION IN SIZE IN NORTH AMERICAN BROWN BEARS, URSUS ARCTOS L., AS INDICATED BY CONDYLOBASAL LENGTH

• Published in: Canadian Journal of Zoology
• Main Author: Rausch, Robert L.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1963
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Arctic; Yukon; Coronation Gulf; Kodiak; Ursus arctos; Alaska
• Online Access: http://dx.doi.org/10.1139/z63-005; http://www.nrcresearchpress.com/doi/pdf/10.1139/z63-005

Variation in size of brown bears, Ursus arctos Linnaeus, indicated by condylobasal length of the skull, has been studied in 357 specimens comprising series from 26 regions in North America. These were selected by criteria defined from a previous study of growth in black bears, U. americanus Pallas, since it was determined that the growth pattern is essentially the same for the two species. Variation in mean condylobasal length in the series studied is clinal; a well-defined gradient exists along the coastal zone from Bella Coola, British Columbia, to the end of the Alaska Peninsula, with mean condylobasal length increasing from south to northwest. A similar gradient was evident along the Arctic Coast, beginning in the region of Coronation Gulf. In the interior, small mean values were obtained for samples from the western Yukon Territory, with mean size increasing toward both the southeast and the northwest. It is concluded that formal recognition of segments of intergrading populations of brown bears at the subspecific level is not justified. Brown bears on Kodiak–Afognak–Shuyak Islands comprise a reproductively isolated population possessing distinctive cranial characteristics, and to them the name U. arctos middendorffi Merriam is applicable. It is proposed that U. a. horribilis Ord be used for brown bears over the greater part of the range of the species in North America. The number of subspecies of U. arctos recognized in Eurasia also may be reduced, with the study of comparable series of skulls.