Foraging strategies by omnivores: are black bears actively searching for ungulate neonates or are they simply opportunistic predators?
Foraging strategies by omnivores: are black bears actively searching for ungulate neonates or are they simply opportunistic predators?
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DOI：
10.1111/j.1600-0587.2010.06517.x
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发表时间：
2011-08-01
期刊：
影响因子：
5.9
通讯作者：
Ouellet, Jean-Pierre
中科院分区：
文献类型：
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作者：
Bastille-Rousseau, Guillaume;Fortin, Daniel;Ouellet, Jean-Pierre
杂食动物以分布动态的动物和分布静态的植物为食。它们所采用的搜寻策略不仅会决定目标猎物的风险，还会决定在遇到其他猎物时可能被其捕食的那些猎物的风险。因此，杂食动物对多猎物系统动态的潜在影响取决于资源选择以及用于寻找猎物的策略。我们提出一种方法，通过结合栖息地选择、局部停留时间和斑块间移动的分析来阐明杂食动物的觅食决策。我们利用这一框架来评估杂食性黑熊对有蹄类幼崽的捕食是源于主动搜寻还是偶然相遇。在产仔季节，我们监测了12只熊、22只森林驯鹿和36只驼鹿。我们利用资源选择函数（RSF）估计了有蹄类幼崽相对出现概率的空间模式。我们还根据植被调查绘制了植物丰度图。然后构建资源选择函数来评估熊的分布与这三种食物类型（植被、驼鹿幼崽、驯鹿幼崽）分布之间的联系。我们通过探究停留时间和斑块间移动的模式，进一步评估了导致这种空间依赖性的熊所使用的搜寻策略。熊没有选择与幼崽相遇概率高的区域，而是选择了植被丰富的区域。令人惊讶的是，熊在植被丰富的区域停留时间较短。因此，对植被丰富区域的选择是通过优先但频繁地在植被丰富的区域之间移动来实现的。这种频繁的斑块间移动可能导致与幼崽的偶然相遇率很高，即使熊没有主动搜寻它们。为了减轻森林采伐对受威胁的驯鹿种群的影响，熊所选择的植被丰富区域（例如路边）应该与适合驯鹿的大片成熟针叶林区分开来。
Omnivores feed on animals with dynamic distributions and on plants with static distributions. The search tactics they adopt will not only define the risk for the targeted prey, but also for other prey that may be consumed when encountered. The potential impact of omnivores on the dynamics of multi-prey systems thus depends on resource selection and on the tactics used to find their prey. We present an approach that can clarify the foraging decisions of omnivores by combining analyses of habitat selection, local residency time, and interpatch movements. We use this framework to evaluate whether predation by omnivorous black bears on ungulate neonates resulted from an active search or from incidental encounters. We monitored 12 bears, 22 forest-dwelling caribou, and 36 moose during calving seasons. We estimated the spatial patterns in relative occurrence probability of ungulate neonates using Resource Selection Functions (RSFs). We also mapped plant abundance from vegetation surveys. RSF were then built to assess the link between bear distribution and the distribution of these three food types (vegetation, moose calves, caribou fawns). We further evaluated the search tactic used by bears that led to this spatial dependency by exploring patterns of residency times and interpatch movements. Bears did not select areas with a high probability of encounter with neonates, but selected areas with abundant vegetation. Surprisingly, bears displayed shorter residency times in vegetation-rich areas. The selection for vegetation-rich areas was therefore achieved by moving preferentially, but frequently, between areas offering abundant vegetation. Such frequent interpatch movements could result in high rates of fortuitous encounters with neonates, even if bears are not actively searching for them. To mitigate the impacts of forest harvesting on threatened caribou populations, vegetation-rich areas selected by bears (e. g. roadsides) should be segregated from large patches of mature conifer forest suitable for caribou.