Data from: Spatiotemporal heterogeneity in prey abundance and vulnerability shapes the foraging tactics of an omnivore

• Main Authors: Rayl, Nathaniel D., Bastille-Rousseau, Guillaume, Organ, John F., Mumma, Matthew A., Mahoney, Shane P., Soulliere, Colleen E., Lewis, Keith P., Otto, Robert D., Murray, Dennis L., Waits, Lisette P., Fuller, Todd K.
• Language: unknown
• Published: 2018
• Subjects: Life sciences; medicine and health care; Canada; Newfoundland; Rangifer tarandus
• Online Access: http://nbn-resolving.org/urn:nbn:nl:ui:13-qh-95mn; https://easy.dans.knaw.nl/ui/datasets/id/easy-dataset:100619

1. Prey abundance and prey vulnerability vary across space and time, but we know little about how they mediate predator-prey interactions and predator foraging tactics. To evaluate the interplay between prey abundance, prey vulnerability, and predator space use, we examined patterns of black bear (Ursus americanus) predation of caribou (Rangifer tarandus) neonates in Newfoundland, Canada using data from 317 collared individuals (9 bears, 34 adult female caribou, 274 caribou calves). 2. During the caribou calving season, we predicted that landscape features would influence calf vulnerability to bear predation, and that bears would actively hunt calves by selecting areas associated with increased calf vulnerability. Further, we hypothesized that bears would dynamically adjust their foraging tactics in response to spatiotemporal changes in calf abundance and vulnerability (collectively, calf availability). Accordingly, we expected bears to actively hunt calves when they were most abundant and vulnerable, but switch to foraging on other resources as calf availability declined. 3. As predicted, landscape heterogeneity influenced risk of mortality, and bears displayed the strongest selection for areas where they were most likely to kill calves, which suggested they were actively hunting caribou. Initially, the per-capita rate at which bears killed calves followed a type-I functional response, but as the calving season progressed and calf vulnerability declined, kill rates dissociated from calf abundance. In support of our hypothesis, bears adjusted their foraging tactics when they were less efficient at catching calves, highlighting the influence that predation phenology may have on predator space use. Contrary to our expectations, however, bears appeared to continue to hunt caribou as calf availability declined, but switched from a tactic of selecting areas of increased calf vulnerability to a tactic that maximized encounter rates with calves. 4. Our results reveal that generalist predators can dynamically adjust ...