DOI: 10.5061/dryad.27sk5
title: Data from: Caribou avoiding wolves face increased predation by bears – caught between Scylla and Charybdis

description: 1. Prey may trade off resource acquisition with mortality risk by using
 various habitat-selection strategies. Empirical assessments have shown
 that the functional and numerical responses of predators to human
 disturbances are variable, yet spatial changes in predation risk by two
 predators have seldom been studied for prey occurring in human-modified
 landscapes. Using the boreal caribou (Rangifer tarandus caribou) – grey
 wolf (Canis lupus) – black bear (Ursus americanus) system in eastern
 Canada, we investigated whether responses of prey towards one predator
 could concomitantly increase risk of predation from another predator
 exhibiting a different foraging tactic. 2. We investigated trade-offs made
 by solitary caribou females and mothers accompanied by their calf during
 the period of highest calf vulnerability, and compared the behaviour of
 mothers that would eventually lose their calf to predation to that of
 mothers whose calf survived until the following year. We modelled habitat
 selection using different metrics of forage based on field measurements
 and digital maps, and developed empirical models of predation risk and
 prey behaviour using GPS data collected on both predators and prey. 3.
 Mothers accompanied by their calf seemed to compromise foraging
 opportunities for safety, as opposed to solitary females who showed no
 particular avoidance of areas used by predators. Although caribou mothers
 adopted selection strategies that could have protected their offspring
 from wolves, females that eventually lost their calf to predation selected
 for vegetative associations that were favourable to bears. 4. Synthesis
 and applications. We determined that mothers that most strongly avoided
 suitable wolf habitat were also those that most strongly selected suitable
 bear habitat, suggesting that by using anti-predator strategies aimed at
 reducing predation risk from wolves, caribou exposed their offspring to
 increased predation risk from bears. This result is of paramount
 conservation value as bears were responsible for 94% of caribou calf kills
 in this system. In the short term, conservation efforts for boreal caribou
 may benefit from the management of bear populations by means of liberal
 hunting regulations or predator control. In the long term, however, these
 actions should be used in conjunction with the protection of potential
 calving areas away from cutblocks and roads.
description: Forage availability in
 caribou rangeHabitat characteristics
 measured in the field to quantify forage availability in the range of the
 Charlevoix caribou population, Québec, Canada,
 2007-2008.Field_surveys.xlsxCaribou dataData set used to measure habitat selection by caribou. The UA variable differentiates use (1) and availability (0). The 3 reproductive statuses are represented by "solitary", "calf_alive", and "calf_dead".Caribou_Data.xlsxWolf dataData set used to measure habitat selection by wolf. The UA variable differentiates use (1) and availability (0).Wolf_Data.xlsxBear dataData set used to measure habitat selection by bear. The UA variable differentiates use (1) and availability (0).Bear_Data.xlsxResults from individual resource selection modelsThe results from the 43 individual RSFs are reported in this table. For each variable, we report the estimate, standard error of the estimate (SE), degrees of freedom (DF), t value, p value (with alpha = 0.05), and lower and upper bounds of the 95% confidence interval (CI95%).Individual_models.xlsx