Alaskan brown bears (Ursus arctos) aggregate and display fidelity to foraging neighborhoods while preying on Pacific salmon along small streams. Issue 17 (19th August 2018)

• Record Type: Journal Article
• Authors: Wirsing, Aaron J.; Quinn, Thomas P.; Cunningham, Curry J.; Adams, Jennifer R.; Craig, Apryle D.; Waits, Lisette P.
• Is Part Of: Ecology and evolution. Volume 8:Issue 17(2018)
• Page Start: 9048
• Page End: 9061
• Publication Date: 2018-08-19
• Subjects: genetic capture‐mark‐recapture -- noninvasive population estimation -- Oncorhynchus nerka -- predation -- sockeye salmon; Ecology -- Periodicals; Evolution -- Periodicals; 577.05
• DOI: 10.1002/ece3.4431
• Languages: English
• ISSNs: 2045-7758

Abstract

Abstract: The interaction between brown bears ( Ursus arctos ) and Pacific salmon ( Oncorhynchus spp.) is important to the population dynamics of both species and a celebrated example of consumer‐mediated nutrient transport. Yet, much of the site‐specific information we have about the bears in this relationship comes from observations at a few highly visible but unrepresentative locations and a small number of radio‐telemetry studies. Consequently, our understanding of brown bear abundance and behavior at more cryptic locations where they commonly feed on salmon, including small spawning streams, remains limited. We employed a noninvasive genetic approach (barbed wire hair snares) over four summers (2012–2015) to document patterns of brown bear abundance and movement among six spawning streams for sockeye salmon, O. nerka, in southwestern Alaska. The streams were grouped into two trios on opposite sides of Lake Aleknagik. Thus, we predicted that most bears would forage within only one trio during the spawning season because of the energetic costs associated with swimming between them or traveling around the lake and show fidelity to particular trios across years because of the benefits of familiarity with local salmon dynamics and stream characteristics. Huggins closed‐capture models based on encounter histories from genotyped hair samples revealed that as many as 41 individuals visited single streams during the annual 6‐week sampling season. Bears also moved freely among trios of streams but rarely moved between these putative foraging neighborhoods, either during or between years. By implication, even small salmon spawning streams can serve as important resources for brown bears, and consistent use of stream neighborhoods by certain bears may play an important role in spatially structuring coastal bear populations. Our findings also underscore the efficacy of noninvasive hair snagging and genetic analysis for examining bear abundance and movements at relatively fine spatial and temporal scales. Abstract : The interaction between brown bears and Pacific salmon is widely recognized, yet most of what we know about the bears involved in this relationship comes from observations at a few highly visible but largely unrepresentative locations and a small number of radio‐telemetry studies. To address this gap in knowledge, we employed a noninvasive genetic approach (barbed wire hair snares) over four summers (2012–2015) to document patterns of brown bear abundance and movement among six streams used as spawning habitat for sockeye salmon, O. nerka, in southwestern Alaska. We documented large bear aggregations, frequent movement among trios of proximate streams on either side of Lake Aleknagik, and infrequent movement between these apparent foraging neighborhoods either during or between years, suggesting that even small salmon spawning streams can serve as important resources for brown bears and consistent use of stream neighborhoods by certain bears may play an important role in spatially structuring coastal bear populations.