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Grizzly Bear Activity Budget and Pattern in the Firth River Valley, Yukon

A. Grant MacHutchon
Ursus
Vol. 12 (2001), pp. 189-198
Stable URL: http://www.jstor.org/stable/3873248
Page Count: 10
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Grizzly Bear Activity Budget and Pattern in the Firth River Valley, Yukon
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Abstract

I determined the activity of 5 radiocollared grizzly bears (Ursus arctos) in the Firth River Valley, Ivvavik National Park, Yukon, Canada, based on 574 hours of direct observation during 1994 and 1995. Radiocollared grizzly bears that were feeding primarily on caribou (Rangifer tarandus) tended to spend less time feeding and more time traveling or resting than bears that were feeding primarily on plants. During most observations bears fed primarily on plants. All bears spent a similar amount of time active (mean 66%, range 59-81%), during which they were primarily feeding or foraging (mean 56%, range 48-62%). For most behaviors, there was no difference among seasons; however, there was a difference for intraspecific behavior. Grizzly bear feeding bouts were longer in summer than fall or spring. In summer with 24 hours of daylight, grizzly bears tended to be most active in the evening and least active when the sun was lowest on the horizon. During fall, with increasing hours of darkness, grizzly bears were least active at night and had peaks of activity in the morning and evening. Grizzly bears in the Firth River Valley were not active more, relative to southern areas, to compensate for their short growing season, despite having more hours of daylight and not being constrained by human disturbance. Bears appeared to meet their energy requirements by acquiring protein and fat from caribou, Artic ground squirrels (spermophilus parryii), and other small mammals. Grizzly bears in the Firth River Valley currently appear to be able to effectively exploit available resources; however, repeated disruptions from human activity have the potential to adversely affect the time available for the acquisition of necessary energy.

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