Influences of cutthroat trout ( Oncorhynchus clarki ) on behaviour and reproduction of Yellowstone grizzly bears ( Ursus arctos ), 1975 – 1989
We investigated the distribution, diet, and reproduction of grizzly bears (Ursus arctos) in the Yellowstone ecosystem that fed on cutthroat trout (Oncorhynchus clarki) spawning in streams tributary to Yellowstone Lake. We hypothesized that availability of trout influenced all of these factors for be...
| Published in: | Canadian Journal of Zoology |
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| Main Authors: | , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Canadian Science Publishing
1995
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.1139/z95-244 http://www.nrcresearchpress.com/doi/pdf/10.1139/z95-244 |
| Summary: | We investigated the distribution, diet, and reproduction of grizzly bears (Ursus arctos) in the Yellowstone ecosystem that fed on cutthroat trout (Oncorhynchus clarki) spawning in streams tributary to Yellowstone Lake. We hypothesized that availability of trout influenced all of these factors for bears in a large part of the Yellowstone grizzly bear recovery area. Depending upon sex, bears that fed on trout used 30–45% of the recovery area. These bears concentrated within 12 km of spawning streams year-round and within 2 km of streams during the spawning season, 1 May – 15 July, when trout-eating bears mostly consumed trout. Despite use of this high-quality food, trout-eating females were apparently less fecund than other females and lost a larger percentage of their dependent young. We speculate that these cub losses resulted from higher rates of intraspecific predation by bears aggregated at spawning streams. These aggregated bears were also vulnerable to human-caused mortality, most likely due to concentrations of humans within 2 km of spawning streams during the spawning season. |
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