Does wolf presence reduce moose browsing intensity in young forest plantations?

Beeck Calkoen, Suzanne T.S. van; Kuijper, Dries P.J.; Sand, Håkan; Singh, Navinder J.; Wieren, Sip E. van; Cromsigt, Joris P.G.M.


Large carnivores can be a key factor in shaping their ungulate prey's behavior, which may affect lower trophic levels. While most studies on trade-offs between food acquisition and risk avoidance by ungulate prey species have been conducted in areas with limited human impact, carnivores are now increasingly returning to highly anthropogenic landscapes. Many of these landscapes are dominated by forestry, and ungulate-forestry conflicts are an increasing issue. The aim of this study was to test if the indirect effects of a re-colonizing large predator, the wolf Canis lupus, results in a change in browsing intensity by moose Alces alces in young forest plantations in a boreal forest in Sweden. We selected 24 different forest plantations, with 12 located in low-wolf and 12 in high-wolf utilization areas. In each plantation, we measured browsing intensity, tree height, tree density, distance to the closest forest edge and we counted the number of moose pellet groups. In contrast to our predictions, wolf utilization was not the main driver of moose browsing patterns. Instead, moose browsing intensity declined with tree density and height. Separate analyses on the main tree species showed that wolf utilization had an influence, but browsing intensity was in fact higher in the high-wolf utilization areas for three out of five tree species. This pattern seemed to be driven by a strong confounding relationship between wolf utilization, tree density and height, which were both lower in the high-wolf utilization areas. We argue that this confounding effect is due to wolves being pushed towards the less productive parts of the landscape away from human activity centers. Therefore, we concluded that in order to better understand carnivore driven risk-mediated effects on herbivore behavior in anthropogenic landscapes we need to better understand the complexity of human-carnivore-prey-ecosystem interactions. Ecography