Direct and indirect effects on moose of wolf return to Scandinavia
Håkan Sand1,
Barbara Zimmermann2,
Camilla Wikenros3,
Petter Wabakken2
Grimsö Wildlife Research Station, SLU, Grimsö forskningsstation, Riddarhyttan, SE
University of Inland Norway
Grimsö Wildlife Research Station, SLU
Abstract Wolves (Canis lupus) returned to central Scandinavia in the 1980’s after population absence of approx. 100 years through natural immigration from the Finnish-Russian population. In the late 1990’s, a formal research project on wolves was initiated (SKANDULV) which included many ecological aspects of wolves and their impact on prey. Early results showed moose (Alces alces) to be the main prey species in most of their distribution area. During this 25-year period, several aspects of moose-wolf interactions have been examined including both direct (predation) and indirect (behavioural) effects on moose.
Results show that wolf predation rate on moose is not related to the density of moose, wolf pack size, nor kill rate but is positively related to wolf density and strongly negatively related to the abundance of moose within wolf territories. Estimated annual wolf predation rates averaged 8.6%, among wolf territories, whereas estimated annual harvest rates averaged 17.5%. In wolf territories with relatively high brown bear (Ursus arctos) densities, the combined predation rates from wolves and brown bears exceeded harvest rates. The re-establishment 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 densities 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.
Wolf-induced effects on moose behaviour seem so far to be non-existent or small in this system. Human-driven habitat heterogeneity, concentration of moose forage to certain habitat types, and the effects of a multiple-predator guild (human harvest and large carnivores) on moose may all contribute to the results found. We conclude that the wolf landscape of fear is likely to have weak behavioural effects on moose in this system.