Sean D. Farley
Karyn D. Rode
Charles T. Robbins
Jennifer K. Fortin
2007
<p><span>We hypothesized that there would be minimal </span><span class="searchword">dietary</span><span> </span><span class="searchword">overlap</span><span> </span><span class="searchword">between</span><span> </span><span class="searchword">sympatric</span><span> brown bears (<i>Ursus arctos</i>) and American black bears (<i>U. americanus</i>) </span><span class="searchword">relative</span><span> to </span><span class="searchword">salmon</span><span> (<i>Oncorhynchus </i>spp.) utilization when alternative foods (e.g., fruits) are abundant. To maximize the chance that we would reject this hypothesis, we examined the diets of brown and black bears known to have visited </span><span class="searchword">salmon</span><span> streams. Species, sex, and individual identification of bears visiting </span><span class="searchword">salmon</span><span> streams were determined by DNA analysis of hair and feces collected in 2002-2004 along those streams. Diets were estimated from fecal residues and stable isotope analyses of hair. Assimilated diets of brown bears were 66.0% (SD = 16.7%) </span><span class="searchword">salmon</span><span>, 13.9% (SD = 7.5%) terrestrial animal matter, and 20.1% (SD = 17.2%) plant matter. Assimilated diets of black bears were 8.0% (SD = 5.4%)</span><span class="searchword">salmon</span><span>, 8.4% (SD = 9.7%) terrestrial animal matter, and 83.6% (SD = 7.7%) plant matter. Male and female brown bears did not differ in either the proportion of </span><span class="searchword">dietary</span><span> salmon, terrestrial animal matter, or plant matter. The relative amounts of fruit residues in the feces of brown bears (87.0%, SD = 15.2%) and black bears (91.8%, SD = 7.2%) did not differ. Both sexes of brown bears visited salmon streams and consumed significant amounts of salmon, but only male American black bears visited streams and then consumed minimal amounts of salmon. Thus, brown bears were largely carnivorous and black bears were largely herbivorous and frugivorous. This reduced dietary overlap relative to salmon and fruit use is understandable in light of the concentrated, defendable nature of salmon in small streams, the widely dispersed, non-defendable nature of abundant fruits, the dominance of brown over black bears, the higher energy requirement of the larger brown bear, and, therefore, the differing ability of the species to efficiently exploit different food resources.</span></p>
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10.2192/1537-6176(2007)18[19:DASOBS]2.0.CO;2
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BioOne Complete
Dietary and spatial overlap between sympatric ursids relative to salmon use
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