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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 antipredator 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. [ABSTRACT FROM AUTHOR]

Unambiguous species identification is fundamental, especially when attempting to study species-specific interactions or management and conservation issues. Current weasel identification methods are based on external and cranial morphology, yet North American weasels show significant geographic variation in size and considerable overlap occurs in measurements of Mustela erminea and M. frenata. As a result, these species can easily be confused. Our objectives were to: (1) develop a simple method based on restriction fragment length polymorphism (RFLP) analyses to classify Mustela spp. in eastern Québec, Canada; (2) validate existing external and cranial morphological criteria in the literature for weasel identification: and (3) calculate discriminant functions based on genetically identified specimens to aid in Mustela identification where genetic laboratory facilities are not readily available. Skeletal and external measurements were taken on adult male Mustela specimens (n〉=〉28) that had been collected in the winter of 2002-2003. Results from genetic analyses confirmed a northern range expansion of long-tailed weasels into Quebec and revealed that current morphological criteria alone are not adequate for classifying Mustela specimens. As many as 18% of Mustela erminea and M. frenata individuals were mis-identified due to morphological measurements, either falling outside known ranges for each species or inside measurement ranges common to both species. [ABSTRACT FROM AUTHOR]