| Summary: | Trophic interactions are a fundamental topic in ecology, but we know little about how competition between apex predators affects predation, the mechanism driving top-down forcing in ecosystems. We used long-term datasets from Scandinavia (Europe) and Yellowstone National Park (North America) to evaluate how grey wolf (Canis lupus) kill rate was affected by a sympatric apex predator, the brown bear (Ursus arctos). We used kill interval (i.e. the number of days between consecutive ungulate kills) as a proxy of kill rate. Although brown bears can monopolize wolf kills, we found no support in either study system for the common assumption that they cause wolves to kill more often. On the contrary, our results showed the opposite effect. In Scandinavia, wolf packs sympatric with brown bears killed less often than allopatric packs during both spring (after bear den emergence) and summer. Similarly, the presence of bears at wolf-killed ungulates was associated with wolves killing less often during summer in Yellowstone. The consistency in results between the two systems suggests that brown bear presence actually reduces wolf kill rate. Our results suggest that the influence of predation on lower trophic levels may depend on the composition of predator communities. Data from wolf predation studies carried out in Scandinavia (2001-2015) and Yellowstone National Park (2008-2015). Excel file of data from wolf predation studies carried out in Scandinavia (2002-2015) and Yellowstone National Park (2008-2015). Data include: study system (Scandinavia or Yellowstone), study season (spring or summer), study year, pack ID (pack name/territory), wolf ID (identity of each wolf followed – Yellowstone only), unique kill ID (identity number associated with each wolf killed carcass – Yellowstone only), kill interval (time to next kill in days), bear presence (Scandinavia – absent or present in the study system; Yellowstone – absent or present at carcass site), Julian date (date of wolf kill), prey type (Scandinavia spring study – ...
|
|---|