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Population-level resource selection by sympatric brown and American black bears in Alaska

TitlePopulation-level resource selection by sympatric brown and American black bears in Alaska
Publication TypeJournal Article
Year of Publication2010
AuthorsBelant, JL, Griffith, B, Zhang, Y, Follmann, EH, Adams, LG
JournalPolar Biology

Distribution theory predicts that for two speciesliving in sympatry, the subordinate species would be constrainedfrom using the most suitable resources (e.g., habitat),resulting in its use of less suitable habitat and spatialsegregation between species. We used negative binomialgeneralized linear mixed models with fixed effects toestimate seasonal population-level resource selection attwo spatial resolutions for female brown bears (Ursusarctos) and female American black bears (U. americanus)in southcentral Alaska during May–September 2000. Blackbears selected areas occupied by brown bears during springwhich may be related to spatially restricted (i.e., restrictedto low elevations) but dispersed or patchy availability offood. In contrast, black bears avoided areas occupied bybrown bears during summer. Brown bears selected areasnear salmon streams during summer, presumably to accessspawning salmon. Use of areas with high berry productionby black bears during summer appeared in response toavoidance of areas containing brown bears. Berries likelyprovided black bears a less nutritious, but adequate foodsource. We suggest that during summer, black bears weredisplaced by brown bears, which supports distributiontheory in that black bears appeared to be partially constrainedfrom areas containing salmon, resulting in theiruse of areas containing less nutritious forage. Spatial segregationof brown and American black bears apparentlyoccurs when high-quality resources are spatially restrictedand alternate resources are available to the subordinatespecies. This and previous work suggest that individualinteractions between species can result in seasonal population-level responses.

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