Brown bear genetic detections as the basis for an analysis of stream use in relation to spawning salmon abundance and stream morphology

Brown bears (Ursus arctos (Linnaeus, 1758)) are famous for exploiting annual pulses of Pacific salmon (Oncorhynchus sp.), but studies of how bears do so have largely been confined to anomalous locations where they congregate to feed at natural salmon migration bottlenecks. We addressed this knowledge gap using nine years of non-invasive genetic detections of brown bears along six small streams – grouped into trios along the northern and southern shores of Lake Aleknagik that constitute foraging neighborhoods where distinct bear populations prey on sockeye salmon (O. nerka (Walbaum, 1792)) – to test hypotheses about sex-specific patterns of relative stream use in relation to salmon abundance and stream morphology. Numbers detections per bear on a stream during the summer salmon spawning season were inversely proportional to water depth in the northern stream neighborhood; by contrast, greater in-stream salmon abundance boosted detection rates, and females were more likely to be detected ..., Field data collection
We quantified use of the six focal streams by bears during the summers of 2013-2019 and 2021-2022 (no data were collected in 2020 because of the coronavirus pandemic) using a non-invasive genetic approach described in detail by Wirsing et al. (2018, 2020). Briefly, over the course of the roughly six-week salmon spawning interval, we collected hair from passing bears by deploying two barbed wires (one upstream and one downstream within the first 2 km from the mouth) crossing each stream perpendicularly at a height of ca. 50-55 cm from the ground (the optimum for snagging hair from bears stepping over or under the wire; Quinn et al. 2022). A video assessment revealed that bears encountering a wire deposited hair ~ 81% of the time (Wold et al. 2020), making this approach an effective, albeit conservative, means of documenting bear presence on a stream, at least in the vicinity of the wires. Hair samples snagged on the wires were collected regularly (usually every othe..., ---

## Title of Dataset: FULL_Bear_hair_detections.2012.2022_2

# Access this dataset on Dryad: DOI:10.5061/dryad.0000000j1

Dataset contents include BearID (from DNA analysis), capture count (i.e., times a bear was detected), year of data collection, stream sampled, focal stream salmon abundance, neighborhood salmon abundance (this was abundance in the adjacent streams and not the focal stream within a neighborhood trio), sex (male or female), stream depth (m), stream width (m), and multiple columns indicating if one,or both, wires were contacted by a given bear.
Non-invasive genetic detections of individual brown bears along salmon spawning streams were used to explore hypotheses about sex-specific patterns of relative stream use in relation to salmon abundance and stream morphology.
Bear detections were modeled separately for northern and southern stream trios of Lake Aleknagik using generalized linear models and generalized linear mixed models with capture count as the response met...,