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

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.

大型食肉动物是调控其有蹄类猎物行为的关键驱动因子，该效应可进一步传递至更低营养级的生态系统组分。尽管现有针对有蹄类猎物在食物获取与风险规避间权衡的研究，多集中于人类干扰较弱的区域，但如今食肉动物正愈发频繁地重返人类活动高度密集的景观。这类景观多由林业用地主导，有蹄类与林业生产间的冲突问题亦日益凸显。本研究旨在检验：在瑞典一处北方针叶林的年轻人工林内，重新定居的大型捕食者灰狼（Canis lupus）所产生的间接效应，是否会改变驼鹿（Alces alces）的树木啃食强度。我们共遴选24处人工林样地，其中12处位于灰狼利用强度较低的区域，剩余12处位于灰狼利用强度较高的区域。在每处样地中，我们均测定了树木啃食强度、树高、林木密度、到最近林缘的距离，并统计了驼鹿粪便团的数量。与研究假设相悖，灰狼利用强度并非驼鹿啃食模式的主要驱动因素。反之，驼鹿的啃食强度随林木密度与树高的增加而降低。针对主要林木树种的单独分析显示，灰狼利用强度确实存在影响：在灰狼利用强度较高的区域，五种树种中有三种的啃食强度反而更高。该模式似乎源于灰狼利用强度、林木密度与树高三者间存在极强的混淆关联——在灰狼利用强度较高的区域，林木密度与树高均处于较低水平。我们认为，这种混淆效应的成因是灰狼被迫迁徙至远离人类活动中心的景观低生产力区域。综上，若要更好地理解人为干扰景观中食肉动物介导的风险对草食动物行为的间接效应，我们需进一步厘清人类-食肉动物-猎物-生态系统间交互作用的复杂性。