Data from: Sociodemographic factors modulate the spatial response of brown bears to vacancies created by hunting

1.There is a growing recognition of the importance of indirect effects from hunting on wildlife populations, e.g., social and behavioral changes due to harvest, which occur after the initial offtake. Nonetheless, little is known about how the removal of members of a population influences the spatial configuration of the survivors.

2.We studied how surviving brown bears (Ursus arctos) used former home ranges that had belonged to casualties of the annual bear hunting season in southcentral Sweden (2007-2015). We used resource selection functions to explore the effects of the casualty's and survivor's sex, age, and their pairwise genetic relatedness, population density, and hunting intensity on survivors’ spatial responses to vacated home ranges.

3.We tested the competitive release hypothesis, whereby survivors that increase their use of a killed bear's home range are presumed to have been released from intraspecific competition. We found strong support for this hypothesis, as survivors of the same sex as the casualty consistently increased their use of its vacant home range. Patterns were less pronounced or absent when the survivor and casualty were of opposite sex.

4.Genetic relatedness between the survivor and the casualty emerged as the most important factor explaining increased use of vacated male home ranges by males, with a stronger response from survivors of lower relatedness. Relatedness was also important for females, but it did not influence use following removal; female survivors used home ranges of higher related female casualties more, both before and after death. Spatial responses by survivors were further influenced by bear age, population density, and hunting intensity.

5.We have showed that survivors exhibit a spatial response to vacated home ranges caused by hunting casualties, even in non-territorial species such as the brown bear. This spatial reorganization can have unintended consequences for population dynamics and interfere with management goals. Altogether, our results underscore the need to better understand the short- and long-term indirect effects of hunting on animal social structure and their resulting distribution in space.

1. 人们日益认识到狩猎对野生动物种群产生的间接效应的重要性，例如狩猎引发的社会与行为改变——这类效应发生在初始捕获之后。然而，目前人们对移除种群个体如何影响存活个体的空间格局仍知之甚少。
2. 我们以瑞典中南部2007年至2015年的年度棕熊狩猎季中，被猎杀个体的原属家域为研究对象，探究了存活棕熊（Ursus arctos）对该类家域的利用情况。我们采用资源选择函数（resource selection functions），分析了猎杀个体与存活个体的性别、年龄、二者的成对遗传亲缘关系、种群密度以及狩猎强度，对存活个体响应空出家域的空间行为的影响。
3. 我们检验了竞争释放假说：即增加对被猎杀熊只家域利用的存活个体，被认为已从种内竞争中获得释放。我们的研究结果为该假说提供了强有力的支持——与猎杀个体同性别的存活个体，始终会提升对其空出的家域的利用。而当存活个体与猎杀个体性别相反时，上述模式则不显著，或根本不存在。
4. 存活个体与猎杀个体间的成对遗传亲缘关系，成为解释雄性个体增加对被猎杀雄性家域利用的最关键因素，且亲缘关系越低的存活个体，其响应程度越强。成对遗传亲缘关系对雌性个体同样重要，但并未对其猎杀后的家域利用产生影响：雌性存活个体无论在猎杀前后，都更倾向于利用亲缘关系更高的雌性猎杀个体的家域。存活个体的空间响应还受到熊只年龄、种群密度以及狩猎强度的进一步影响。
5. 我们的研究表明，即使在棕熊这类非领地性物种中，存活个体也会对狩猎猎杀导致的空出家域产生空间响应。这类空间重构可能会对种群动态产生意想不到的后果，并干扰野生动物管理目标的实现。综上，我们的研究结果强调，亟需更深入地理解狩猎对动物社会结构及其最终空间分布产生的短期与长期间接效应。