Sysiak Monika, Maszczyk Piotr, Mikulski Andrzej
Department of Hydrobiology, Institute of Ecology, Faculty of Biology, University of Warsaw, Żwirki i Wigury 101, Warsaw 02-089, Poland.
R Soc Open Sci. 2025 Jan 22;12(1):241711. doi: 10.1098/rsos.241711. eCollection 2025 Jan.
Many studies have shown that prey can optimize their defence mechanisms based on cues indicating predator presence and pressure. However, little is known about whether prey can assess the actual threat by considering both predator density and the motivational state of cannibalistic predators, which can be influenced by threats from higher order predators. We conducted laboratory experiments to test the hypothesis that high predator density, combined with chemical cues indicating predator stress (e.g. alarm and disturbance cues), may inhibit prey defences. Using and Zygoptera/Anisoptera larvae, we observed that strong response to low-density predator kairomones was suppressed when exposed to high-density predator kairomones and disturbance cues. Surprisingly, we found no evidence of a suppressive response to alarm cues. Our study is to our knowledge, the first to show that prey uses predator stress cues to avoid unnecessary defences, suggesting a 'cascade of fear' in which fear at one trophic level reduces fear at a lower level. Furthermore, it is to our knowledge the first to demonstrate that prey can reduce their anti-predator response in the presence of high densities of cannibalistic predators.
许多研究表明，猎物能够根据表明捕食者存在和压力的线索来优化其防御机制。然而，对于猎物是否能够通过考虑捕食者密度和同类相食捕食者的动机状态来评估实际威胁，人们却知之甚少，而同类相食捕食者的动机状态可能会受到来自更高阶捕食者的威胁的影响。我们进行了实验室实验，以检验这样一个假设：高捕食者密度，再加上表明捕食者压力的化学线索（如警报和干扰线索），可能会抑制猎物的防御。使用蜻蜓目幼虫和差翅亚目/均翅亚目幼虫，我们观察到，当暴露于高密度捕食者信息素和干扰线索时，对低密度捕食者信息素的强烈反应会受到抑制。令人惊讶的是，我们没有发现对警报线索有抑制反应的证据。据我们所知，我们的研究首次表明猎物利用捕食者压力线索来避免不必要的防御，这表明存在一种“恐惧级联”，即一个营养级的恐惧会降低较低营养级的恐惧。此外，据我们所知，这也是首次证明猎物在存在高密度同类相食捕食者的情况下能够降低其反捕食反应。
