Top-down and bottom-up influences on demographic rates of Antarctic fur seals Arctocephalus gazella.
Top-down and bottom-up influences on demographic rates of Antarctic fur seals Arctocephalus gazella.
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自上而下和自下而上对南极海狗种群比例的影响。
DOI：
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发表时间：
2013
影响因子：
4.8
通讯作者：
A. Kilpatrick
中科院分区：
文献类型：
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作者：
L. Schwarz;M. Goebel;Daniel P. Costa;A. Kilpatrick
种群动态的两个主要驱动因素是自下而上的过程，例如影响觅食成功的环境因素，以及捕食的自上而下的影响。由于气候变化自下而上的影响导致猎物减少，许多海洋哺乳动物和海鸟的数量似乎正在下降。然而，通常发生在海上且难以观察的捕食也可能发挥着关键作用。我们分析了 1997 年至 2009 年间 Shirreff 角的南极海狗 Arctocephalus 瞪羚种群动态的驱动因素，包括以断奶前幼崽为目标的捕食者，以及对温度微小变化特别敏感的生态系统中自下而上的环境影响。我们使用贝叶斯标记重捕获分析来证明，尽管大规模的环境变化会影响成年成年动物的年生存率和繁殖率，但第一年生存率似乎正在推动当前种群数量的下降（定义为每年出生的幼崽数量下降）。尽管在研究的前三分之一期间幼崽的数量有所增加，但这些幼崽的第一年存活率和后来几年的招募量都非常低。如此低的存活率可能是由于豹海豹的捕食行为造成的，特别是在断奶之前。我们的研究结果表明，如果没有豹海豹的捕食，尽管观察到气候变化对成年海豹的生命率有自下而上的影响，但该种群的数量很可能会增加。更广泛地说，我们的结果表明，针对年龄的捕食可能是 K 选择的殖民繁殖者种群数量下降的一个主要因素。
Two major drivers in population dynamics are bottom-up processes, such as environmental factors that affect foraging success, and the top-down impacts of predation. Many populations of marine mammal and seabird species appear to be declining in response to reductions in prey associated with the bottom-up effects of climate change. However, predation, which usually occurs at sea and is difficult to observe, may also play a key role. We analysed drivers of population dynamics of Antarctic fur seals Arctocephalus gazella at Cape Shirreff from 1997 to 2009, including a predator that targets pre-weaned pups and bottom-up environmental effects in an ecosystem particularly sensitive to small changes in temperature. We use Bayesian mark-recapture analysis to demonstrate that although large-scale environmental variability affects annual adult survival and reproduction, first year survival appears to be driving the current decline in this population (as defined by a decline in the annual number of pups born). Although the number of pups increased during the first third of the study, first year survival and recruitment of those pups in later years was very low. Such low survival may be driven by leopard seal Hydrurga leptonyx predation, particularly prior to weaning. Our results suggest that without leopard seal predation, this population would most likely increase in size, despite the observed bottom-up effects of climate changes on adult vital rates. More broadly, our results show how age-targeted predation could be a major factor in population decline of K-selected colonial breeders.