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专制行为或觅食行为能解释欧洲出现问题棕熊的原因吗?

Does despotic behavior or food search explain the occurrence of problem brown bears in Europe?

作者信息

Elfström Marcus, Zedrosser Andreas, Jerina Klemen, Støen Ole-Gunnar, Kindberg Jonas, Budic Lara, Jonozovič Marko, Swenson Jon E

机构信息

Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences Postbox 5003, NO-1432, Ås, Norway.

Department of Environmental and Health Studies, Telemark University College NO-3800, Bø i Telemark, Norway ; Institute of Wildlife Biology and Game Management, Department of Integrative Biology and Biodiversity Research, University of Natural Resources and Applied Life Sciences Gregor-Mendel-Str. 33, A-1180, Vienna, Austria.

出版信息

J Wildl Manage. 2014 Jul;78(5):881-893. doi: 10.1002/jwmg.727. Epub 2014 Jun 24.

Abstract

Bears foraging near human developments are often presumed to be responding to food shortage, but this explanation ignores social factors, in particular despotism in bears. We analyzed the age distribution and body condition index (BCI) of shot brown bears in relation to densities of bears and people, and whether the shot bears were killed by managers (i.e., problem bears;  = 149), in self-defense ( = 51), or were hunter-killed nonproblem bears ( = 1,896) during 1990-2010. We compared patterns between areas with (Slovenia) and without supplemental feeding (Sweden) of bears relative to 2 hypotheses. The food-search/food-competition hypothesis predicts that problem bears should have a higher BCI (e.g., exploiting easily accessible and/or nutritious human-derived foods) or lower BCI (e.g., because of food shortage) than nonproblem bears, that BCI and human density should have a positive correlation, and problem bear occurrence and seasonal mean BCI of nonproblem bears should have a negative correlation (i.e., more problem bears during years of low food availability). Food competition among bears additionally predicts an inverse relationship between BCI and bear density. The safety-search/naivety hypothesis (i.e., avoiding other bears or lack of human experience) predicts no relationship between BCI and human density, provided no dietary differences due to spatiotemporal habitat use among bears, no relationship between problem bear occurrence and seasonal mean BCI of nonproblem bears, and does not necessarily predict a difference between BCI for problem/nonproblem bears. If food competition or predation avoidance explained bear occurrence near settlements, we predicted younger problem than nonproblem bears and a negative correlation between age and human density. However, if only food search explained bear occurrence near settlements, we predicted no relation between age and problem or nonproblem bear status, or between age and human density. We found no difference in BCI or its variability between problem and nonproblem bears, no relation between BCI and human density, and no correlation between numbers of problem bears shot and seasonal mean BCI for either country. The peak of shot problem bears occurred from April to June in Slovenia and in June in Sweden (i.e., during the mating period when most intraspecific predation occurs and before fall hyperphagia). Problem bears were younger than nonproblem bears, and both problem and nonproblem bears were younger in areas of higher human density. These age differences, in combination with similarities in BCI between problem and nonproblem bears and lack of correlation between BCI and human density, suggested safety-search and naïve dispersal to be the primary mechanisms responsible for bear occurrence near settlements. Younger bears are less competitive, more vulnerable to intraspecific predation, and lack human experience, compared to adults. Body condition was inversely related to the bear density index in Sweden, whereas we found no correlation in Slovenia, suggesting that supplemental feeding may have reduced food competition, in combination with high bear harvest rates. Bears shot in self-defense were older and their BCI did not differ from that of nonproblem bears. Reasons other than food shortage apparently explained why most bears were involved in encounters with people or viewed as problematic near settlements in our study.

摘要

在人类活动区域附近觅食的熊通常被认为是对食物短缺做出的反应,但这种解释忽略了社会因素,尤其是熊之间的专制行为。我们分析了被射杀棕熊的年龄分布和身体状况指数(BCI),并将其与熊和人类的密度相关联,同时分析了在1990 - 2010年期间,被射杀的熊是被管理人员捕杀(即问题熊;n = 149)、出于自卫被杀死(n = 51),还是被猎人杀死的非问题熊(n = 1896)。我们根据两个假设,比较了有(斯洛文尼亚)和没有(瑞典)对熊进行补充投喂地区的模式。食物搜索/食物竞争假设预测,问题熊的BCI应该比非问题熊更高(例如,利用容易获取和/或营养丰富的人类提供的食物)或更低(例如,由于食物短缺),BCI与人类密度应该呈正相关,问题熊的出现与非问题熊的季节性平均BCI应该呈负相关(即食物可获得性低的年份问题熊更多)。熊之间的食物竞争还预测BCI与熊的密度呈反比关系。安全搜索/天真假设(即避开其他熊或缺乏人类经验)预测,只要熊之间因时空栖息地利用不存在饮食差异,BCI与人类密度就没有关系,问题熊的出现与非问题熊的季节性平均BCI没有关系,并且不一定预测问题/非问题熊的BCI存在差异。如果食物竞争或避免被捕食解释了熊在定居点附近的出现,我们预测问题熊比非问题熊更年轻,且年龄与人类密度呈负相关。然而,如果只有食物搜索解释了熊在定居点附近的出现,我们预测年龄与问题熊或非问题熊的状态之间没有关系,年龄与人类密度之间也没有关系。我们发现问题熊和非问题熊在BCI或其变异性方面没有差异,BCI与人类密度没有关系,两个国家被射杀的问题熊数量与季节性平均BCI之间也没有相关性。在斯洛文尼亚,被射杀的问题熊数量高峰出现在4月至6月,在瑞典出现在6月(即交配期,此时种内捕食最为频繁,且在秋季暴食之前)。问题熊比非问题熊更年轻,在人类密度较高的地区,问题熊和非问题熊都更年轻。这些年龄差异,再加上问题熊和非问题熊在BCI上的相似性以及BCI与人类密度缺乏相关性,表明安全搜索和天真扩散是熊在定居点附近出现的主要机制。与成年熊相比,年轻熊竞争力较弱,更容易受到种内捕食,且缺乏人类经验。在瑞典,身体状况与熊密度指数呈反比关系,而在斯洛文尼亚我们未发现相关性,这表明补充投喂可能与高熊捕获率相结合,减少了食物竞争。出于自卫被射杀的熊年龄更大,其BCI与非问题熊没有差异。在我们的研究中,显然除了食物短缺之外的其他原因解释了为什么大多数熊会与人类发生接触或在定居点附近被视为有问题。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/e242/4140552/bc12eadce258/jwmg0078-0881-f1.jpg

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