Competition between apex predators? Brown bears decrease wolf kill rate on two continents.
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.
Department of Wildland Resources and Ecology Center, Utah State University, 5230 Old Main Hill, Logan, UT 84322, USA aimeetmt@gmail.com.|Grimsö Wildlife Research Station, Department of Ecology, Swedish University of Agricultural Sciences, 730 91 Riddarhyttan, Sweden.
Aimee
0000-0002-7182-7377
A
Tallian
Grimsö Wildlife Research Station, Department of Ecology, Swedish University of Agricultural Sciences, 730 91 Riddarhyttan, Sweden.|Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Postbox 5003, 1432 Ås, Norway.
Andrés
A
Ordiz
Wildlife Biology Program, Department of Ecosystem and Conservation Sciences, University of Montana, Missoula, MT 59812, USA.|Yellowstone Center for Resources, Yellowstone National Park, Box 168, Mammoth Hot Springs, WY 82190, USA.
Matthew C
MC
Metz
Faculty of Applied Ecology and Agricultural Sciences, Inland Norway University of Applied Sciences, Evenstad, 2480 Koppang, Norway.
Cyril
C
Milleret
Grimsö Wildlife Research Station, Department of Ecology, Swedish University of Agricultural Sciences, 730 91 Riddarhyttan, Sweden.
Camilla
C
Wikenros
Yellowstone Center for Resources, Yellowstone National Park, Box 168, Mammoth Hot Springs, WY 82190, USA.
Douglas W
DW
Smith
Yellowstone Center for Resources, Yellowstone National Park, Box 168, Mammoth Hot Springs, WY 82190, USA.
Daniel R
DR
Stahler
Department of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Sciences, 901 83 Umeå, Sweden.|Norwegian Institute for Nature Research, 7485 Trondheim, Norway.
Jonas
J
Kindberg
Department of Wildland Resources and Ecology Center, Utah State University, 5230 Old Main Hill, Logan, UT 84322, USA.
Daniel R
DR
MacNulty
Faculty of Applied Ecology and Agricultural Sciences, Inland Norway University of Applied Sciences, Evenstad, 2480 Koppang, Norway.
Petter
P
Wabakken
Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Postbox 5003, 1432 Ås, Norway.|Norwegian Institute for Nature Research, 7485 Trondheim, Norway.
Jon E
JE
Swenson
Grimsö Wildlife Research Station, Department of Ecology, Swedish University of Agricultural Sciences, 730 91 Riddarhyttan, Sweden.
Håkan
H
Sand
D000818:Animals; D003163:Competitive Behavior; D003670:Deer; D020387:Food Chain; D009656:North America; D011235:Predatory Behavior; D012537:Scandinavian and Nordic Countries; D001503:Ursidae; D019596:Wolves
Canis lupus; Scandinavia; Ursus arctos; Yellowstone; competition; predation