Quantifying large carnivore predation relative to human harvest on moose in an intensively managed boreal ecosystem

Abstract

The return of large carnivores to areas with strong anthropogenic impact often results in conflicts among different interest groups. One cause of conflict is that large carnivores compete with humans for wild game species. In Scandinavia, the recolonization of wolves (Canis lupus) and brown bears (Ursus arctos) has important ramifications for the harvest of an ungulate species with high economic and recreational value, the moose. We estimated wolf and brown bear predation rates on moose (Alces alces) relative to harvest, natural causes of death, and vehicle collisions within 20 wolf territories. We used data on multi-season kill rates of wolves and brown bears on moose combined with wolf territory sizes and estimates of the population density of brown bears and moose. Wolf predation rate on moose was not related to the density of moose, wolf pack size, nor kill rate but was positively related to wolf density and strongly negatively related to the abundance of moose within wolf territories. Estimated annual wolf and brown bear predation rates averaged 8.6% (range 2.8%–16.9%) and 2.3% (range 0%–12.7%) respectively, among wolf territories, whereas estimated annual harvest rates averaged 17.5% (range 8.1%–33.1%). In wolf territories with relatively high bear densities, the combined predation rates from wolves and brown bears exceeded harvest rates. Across wolf territories, harvest rates were not related to wolf predation rates or to the combined predation rates from wolves and brown bears, indicating that large carnivore predation and harvest were not compensatory to each other at this spatial level. The recolonization of these large carnivores in the Scandinavian boreal forest ecosystem may have small to significant consequences for the sustainable management of moose populations depending on the local conditions of both wolves, brown bears, and moose. Comparison of annual mortality rates for moose in our study in Scandinavia with corresponding data from areas with lower anthropogenic impact (Alaska) shows lower total mortality rates in Scandinavia. This likely results from a different age and sex composition of moose killed by wolves and brown bears versus harvest, in combination with a significant difference in the relative importance of these mortality factors between areas.