Data from: Habitat segregation between brown bears and gray wolves in a human-dominated landscape

Identifying how sympatric species belonging to the same guild coexist is a major question of community ecology and conservation. Habitat segregation between two species might help reduce the effects of interspecific competition and apex predators are of special interest in this context, because their interactions can have consequences for lower trophic levels. However, habitat segregation between sympatric large carnivores has seldom been studied. Based on monitoring of 53 brown bears (Ursus arctos) and 7 sympatric adult gray wolves (Canis lupus) equipped with GPS collars in Sweden, we analyzed the degree of interspecific segregation in habitat selection within their home ranges in both late winter and spring, when their diets overlap the most. We used the K-select method, a multivariate approach that relies on the concept of ecological niche, and randomization methods to quantify habitat segregation between bears and wolves. Habitat segregation between bears and wolves was greater than expected by chance. Wolves tended to select for moose occurrence, young forests, and rugged terrain more than bears, which likely reflects the different requirements of an omnivore (bear) and an obligate carnivore (wolf). However, both species generally avoided human-related habitats during daytime. Disentangling the mechanisms that can drive interspecific interactions at different spatial scales is essential for understanding how sympatric large carnivores occur and coexist in human-dominated landscapes, and how coexistence may affect lower trophic levels. The individual variation in habitat selection detected in our study may be a relevant mechanism to overcome intraguild competition and facilitate coexistence.探明同域物种（sympatric species）所属同资源集团（guild）的共存机制，是群落生态学（community ecology）与保护科学的核心议题。两个物种间的生境分化（habitat segregation）有助于减轻种间竞争（interspecific competition）的影响，而顶级捕食者（apex predators）在此类研究中尤为受关注，因为它们的种间相互作用会对较低营养级（trophic levels）的类群产生连锁效应。不过，针对同域分布的大型食肉动物的生境分化研究却鲜有开展。本研究基于瑞典境内佩戴GPS项圈（GPS collars）的53头棕熊（Ursus arctos）与7头同域分布的成年灰狼（Canis lupus）的监测数据，分析了二者在晚冬与春季两个食性重叠度最高的时期内，家域（home ranges）内部生境选择的种间分化程度。我们采用依托生态位（ecological niche）概念构建的多元分析方法——K选择法（K-select method），以及随机化方法（randomization methods），量化棕熊与灰狼间的生境分化程度。研究结果显示，棕熊与灰狼间的生境分化程度显著高于随机预期水平。相较于棕熊，灰狼更倾向于选择驼鹿（moose）分布区、幼龄林（young forests）与崎岖地形（rugged terrain），这大概率契合了杂食动物（omnivore）与专性食肉动物（obligate carnivore）各自的生存需求差异。不过，二者在日间活动时均会避开与人类活动相关的生境。厘清不同空间尺度（spatial scales）下驱动种间相互作用的机制，对于理解同域分布的大型食肉动物如何在人类主导的景观（human-dominated landscapes）中存续并实现共存，以及这种共存如何影响较低营养级的类群，均至关重要。本研究中检测到的生境选择个体差异，或许是克服集团内竞争（intraguild competition）、促进物种共存的关键机制之一。