Density-dependent increase in superpredation linked to food limitation in a recovering population of northern goshawks Accipiter gentilis
Density-dependent increase in superpredation linked to food limitation in a recovering population of northern goshawks Accipiter gentilis
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DOI：
10.1111/jav.01387
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发表时间：
2017-09-01
影响因子：
1.7
通讯作者：
Lambin, X.
中科院分区：
文献类型：
--
作者：
Hoy, S. R.;Petty, S. J.;Lambin, X.
更好地理解超级捕食的驱动机制--较大的顶端捕食者杀死较小的中层捕食者--是很重要的，因为超级捕食在构建群落中可以发挥关键作用，而且它往往涉及保护关切的物种。在这里，我们记录了超级捕食的程度是如何随着时间的推移而变化的，并利用从典型的鸟类超级捕食者--北方苍鹰Accipiter gentilis恢复的种群收集的40年的饮食数据，评估了这种时间变化对当地中掠食者种群的影响。然后，我们评估了哪些机制推动了超级捕食的变化，例如，它是机会主义的，是对食物变得有限的反应(由于首选猎物的减少)，还是为了减少竞争。在苍鹰丰度较高的年份，猛禽平均占苍鹰食物的8%，高于其他地方的报道。此外，随着苍鹰的恢复，人均超级捕食增加，苍鹰食物中猛禽的比例从2%增加到8%，苍鹰栖息地的数量从14个增加到25个。这种超级捕食的增加与最常被捕杀的中掠食性动物--欧亚红隼的种群数量下降相吻合，这可能代表着在苍鹰和其他大型猛禽减少或灭绝后发生的中掠食者释放过程(即中捕食者抑制)的逆转。在这个系统中，食物限制是最可能的超级捕食驱动因素：1)苍鹰食物中两个主要猎物群体的大幅减少，食物多样性的增加和苍鹰繁殖成功率的下降都与苍鹰种群变得食物有限一致；2)这不太可能是纯粹的机会主义，因为超级捕食的增加并没有反映中掠食者物种可获得性的变化；以及3)大多数被苍鹰杀死的中观捕食者并不与苍鹰争夺食物或巢穴。
A better understanding of the mechanisms driving superpredation, the killing of smaller mesopredators by larger apex predators, is important because of the crucial role superpredation can play in structuring communities and because it often involves species of conservation concern. Here we document how the extent of superpredation has changed over time, and assessed the impact of such temporal variation on local mesopredator populations using 40 yr of dietary data collected from a recovering population of northern goshawks Accipiter gentilis, an archetypical avian superpredator. We then assessed which mechanisms were driving variation in superpredation, e.g. was it opportunistic, a response to food becoming limited (due to declines in preferred prey) or to reduce competition. Raptors comprised 8% of goshawk diet on average in years when goshawk abundance was high, which is higher than reported elsewhere. Additionally, there was a per capita increase in superpredation as goshawks recovered, with the proportion of goshawk diet comprising raptors increasing from 2 to 8% as the number of goshawk home-ranges increased from 14 to 25. This increase in superpredation coincided with a population decline in the most commonly killed mesopredator, the Eurasian kestrel Falco tinnunculus, which may represent the reversal of the mesopredator release' process (i.e. mesopredator suppression) which occurred after goshawks and other large raptors declined or were extirpated. Food limitation was the most likely driver of superpredation in this system given: 1) the substantial decline of two main prey groups in goshawk diet, the increase in diet diversity and decrease in goshawk reproductive success are all consistent with the goshawk population becoming food-limited; 2) it's unlikely to be purely opportunistic as the increase in superpredation did not reflect changes in the availability of mesopredator species; and 3) the majority of mesopredators killed by goshawks do not compete with goshawks for food or nest sites.