2019-08-14, Latham, A. David M., Boutin, Stan

Woodland caribou (Rangifer tarandus caribou) in northeastern Alberta have historically been provided a refuge from wolf (Canis lupus) predation by using habitats not typically occupied by moose (Alces alces), which are the primary prey species for wolves in this region. However, in recent years most caribou populations in northeastern Alberta have declined, suggesting that they no longer have a refuge from wolf predation. I tested the hypotheses that (1) primary prey densities have increased since recent industrial expansion into caribou range, resulting in a numeric response by wolves; and (2) an altered wolf-primary prey system has reduced the ability of caribou to spatially separate from other prey - and consequently wolves - in this system. My results showed that wolf densities in the region have increased from approximately 6/1,000 km2 to approximately 11/1,000 km2. Based on my estimates, there has also been a corresponding increase in ungulate biomass, which appears to be primarily due to the recent increase in white-tailed deer (Odocoileus virginianus). My results suggest that wolf use and selection of this novel prey species has also increased dramatically, particularly during the snow season. Similarly, I found that wolf use and selection for beaver (Castor canadensis) was substantively higher than suggested by previous studies in this region. Wolf use of beaver was highest in the snow-free season, and could result in increased wolf-caribou encounters at this time of year. Moose were an important prey species for wolves throughout the year. These results suggest that wolves within caribou range in northeastern Alberta currently utilize multiple primary prey species. The spatial overlap between wolves and caribou has increased substantively within the past decade; however, caribou still attempt to avoid high predation risk by spatially separating from areas that tend to be selected by primary prey species and wolves. Despite differential habitat selection, the proportion of caribou in wolf diet appears to have increased in the past decade, suggesting that bog-fen habitat provides only a partial refuge from predation. These findings are integral to the effective management of primary prey and wolves in caribou ranges in northeastern Alberta, and will help inform caribou landscape planning teams in decision making processes.

2025-08-28, Hebblewhite, Mark

While migration is hypothesized to reduce predation risk for ungulates, there have been few direct empirical tests of this hypothesis. Furthermore, few studies examined multiscale predation risk avoidance by migrant ungulates, yet recent research reveals that predator–prey interactions occur at multiple scales. We test the predation risk reduction hypothesis at two spatial scales in a partially migratory elk (Cervus elaphus) population by comparing exposure of migrant and resident elk to wolf (Canis lupus) predation risk. We used GPS and VHF telemetry data collected from 67 migrant and 44 resident elk over the summers of 2002–2004 in and adjacent to Banff National Park (BNP), Canada. We used wolf GPS and VHF telemetry data to estimate predation risk as a function of the relative probability of wolf occurrence weighted by a spatial density model that adjusted for varying pack sizes. We validated the predation risk model using independent data on wolf-killed elk, and showed that combining wolf presence and spatial density best predicted where an elk was likely to be killed. Predation risk on summer ranges of migrant elk was reduced by 70% compared to within resident elk summer ranges. Because wolves avoided areas near high human activity, however, fine-scale selection by resident elk for areas near high human activity reduced their predation risk exposure to only 15% higher than migrants, a difference significant in only one of three summers. Finally, during actual migration, elk were exposed to 1.7 times more predation risk than residents, even though migration was rapid. Our results support the hypothesis that large-scale migrations can reduce predation. However, we also show that where small-scale spatial variation in predation risk exists, nonmigratory elk may equally reduce predation risk as effectively as migrants under some circumstances.