Fear at the top: killer whale predation drives white shark absence at South Africa's largest aggregation site
Fear at the top: killer whale predation drives white shark absence at South Africa's largest aggregation site
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DOI：
10.2989/1814232x.2022.2066723
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发表时间：
2022-04-03
影响因子：
1.2
通讯作者：
Smale, M. J.
中科院分区：
文献类型：
--
作者：
Towner, A., V;Watson, R. G. A.;Smale, M. J.
在陆地和海洋系统中，顶级捕食者的风险恐惧效应普遍存在，并对生态系统的结构和功能产生持久的影响。顶级捕食者的消失会破坏生态系统并引发营养级联，但将新的顶级捕食者引入生态系统还不是很清楚。我们记录了白鲨Carcharodon carcharias的迁徙，以应对一对虎鲸Orcinus orca的出现，在南非的一个大型白鲨聚集地。2017年2月至6月期间，西开普省甘斯拜的海滩上被冲上了5具白鲨尸体，其中4具被切除了肝脏。每单位努力（海天）的目击数据和遥测数据表明，白鲨在这些捕食事件发生后从甘斯拜迁徙，并对这对和附近其他虎鲸群的进一步目击作出反应。标记数据显示白鲨立即离开甘斯拜，一些鲨鱼随后向东移动。与预期和有充分记录的白鲨出现模式相反，在接下来的2.5年里，白鲨的出现次数下降了；对这两个数据集的变化点分析证实，这些离开与虎鲸的出现和鲨鱼尸体被冲走的时间一致。这些发现表明，大白鲨对来自一种新型捕食者的风险反应迅速，它们的消失引发了另一种捕食者——青铜捕鲸Carcharhinus brachyurus的出现。在南非，白鲨、其他沿海鲨鱼和虎鲸之间的捕食者-猎物相互作用正在增加，预计将对生态系统产生显著影响。
Risk-induced fear effects exerted by top predators are pervasive in terrestrial and marine systems, with lasting impacts on ecosystem structure and function. The loss of top predators can disrupt ecosystems and trigger trophic cascades, but the introduction of novel apex predators into ecosystems is not well understood. We documented the emigration of white sharks Carcharodon carcharias in response to the presence of a pair of killer whales, Orcinus orca, at a large white shark aggregation site in South Africa. Between February and June in 2017, five white shark carcasses washed up on beaches in Gansbaai, Western Cape Province, four of which had their livers removed. Sightings per unit effort (sea days) and telemetry data demonstrated that white sharks emigrated from Gansbaai following these predation events, and in response to further sightings of this pair and other killer whale pods in the vicinity. Tagging data demonstrated the immediate departure of white sharks from Gansbaai, and some sharks were subsequently moving east. Contrary to expected and well-documented patterns of white shark occurrence at this site, their sightings dropped throughout the following 2.5 years; change-point analysis on both datasets confirmed these departures coincided with killer whale presence and shark carcasses washing out. These findings suggest that white sharks respond rapidly to risk from a novel predator, and that their absence triggered the emergence of another predator, the bronze whaler Carcharhinus brachyurus. Predator-prey interactions between white sharks, other coastal sharks, and killer whales are increasing in South Africa and are expected to have pronounced impacts on the ecosystem.