Abstract
AbstractAs wild ungulate densities increase across Europe and North America, plant–herbivore interactions are increasingly important from ecological and economic perspectives. These interactions are particularly significant where agriculture and forestry occur and where intensive grazing and browsing by wild ungulates can result in economic losses to growing crops and trees. We studied plant–herbivore interactions in a moose (Alces alces)‐dominant system where forestry is a primary economy, the primary and secondary road networks are extensive, and wolves (Canis lupus) are recolonizing. Wolves and humans use low‐traffic, secondary roads, yet roadsides provide high‐quality and quantity browse for moose. Foraging theory predicts that moose will respond to riskier landscapes by selecting habitats that reduce predation risk, sacrificing feeding time or food quality. As food becomes limiting, however, animals will accept higher predation risk in search of food. We predicted that road avoidance behavior would be strongest within wolf territories. In areas without wolves, moose should select roadsides for their high forage availability. To test these predictions, we measured moose browsing and counted pellet groups as a proxy for habitat use each spring in Norway and Sweden between 2008 and 2018, in areas with and without wolves and at different distances from primary and secondary roads. We used generalized linear mixed models to evaluate drivers of the probability of browsing occurrence and browsing pressure. We found that browsing occurrence increased closer to secondary roads but decreased closer to primary roads. We also found browsing patterns to vary among tree species. For Scots pine (Pinus sylvestris), the browsing occurrence was two times higher in young forests relative to non‐young forests and decreased further from secondary roads. Wolf territory presence and probability had neutral or positive effect on browsing occurrence and pressure for all species. However, wolf territory presence had negative effects on browsing occurrence and pressure when interacting with secondary roads, young forest, or snow cover. We showed that roads can influence browsing patterns in Norway and Sweden. However, further research is needed, particularly in the face of continued infrastructure development in Scandinavia.
Highlights
Predation can have direct, lethal consequences to prey density and abundance (Gasaway et al 1992, Messier 1994)
We studied plant–herbivore interactions in a moose (Alces alces)-dominant system where forestry is a primary economy, the primary and secondary road networks are extensive, and wolves (Canis lupus) are recolonizing
We tested the importance of roads, young forests, and wolves on moose browsing occurrence and browsing pressure at a fine spatial scale and large spatial extent
Summary
Lethal consequences to prey density and abundance (Gasaway et al 1992, Messier 1994). Prey can perceive predation risk from predators such as large carnivores and humans. There is often a trade-off between predation risk and food supply (Schmitz 2005) and ungulate prey move to vegetative cover in response to predators (Mysterud and Østbye 1999, Creel et al 2005). We can expect that the spatial effects of predators on ungulate browsing patterns will be altered due to predator movements (behaviorally mediated trophic cascades; Schmitz et al 1997). Large carnivores have become threatened globally (Ripple et al 2014) and humans have a disproportionately large effect (direct and indirect) on wildlife behavior and mortality outside of protected areas. Trophic cascades appear more difficult to elucidate outside protected areas (van Beeck Calkoen et al 2018), which could have consequences to predator/prey relationships
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