Caribou avoiding wolves face increased predation by bears – caught between Scylla and Charybdis

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 sel...