Data from: Playing it safe? behavioural responses of mosquito larvae encountering a fish predator

Predation is a strong selective force that affects prey population and ecosystem dynamics. Detecting predators and associated levels of threat is crucial to prey responses. Once a predator is detected, anti-predatory responses improve the chances of survival of prey. We used Aedes aegypti larvae to study behavioural responses to predation threat from guppies (Poecilia reticulata). Specifically, we tested the relative importance of chemical cues, both in isolation and in combination with physical cues, in eliciting anti-predatory behaviours. Larvae responded more strongly, by reducing the lengths of their wriggle bursts, when presented with a combination of chemical and physical cues than with chemical cues alone. Anti-predatory responses often come with an associated cost, and we expect that the ability to pay these costs should influence responses to predation risk. To test this, we compared wriggling patterns of satiated vs starved larvae in the same experiment. We found that, under predation risk, starved larvae were willing to take more risks than satiated larvae were. We sought to experimentally test the assumption that anti-predator behaviours increase the survival of prey. To do this, starved guppies were made to choose between displays of simulated larvae, moving in short and long wriggle bursts as observed in the previous experiment. The fish preferentially attacked larvae moving in long bursts, demonstrating the survival value of the larval anti-predatory response of shifting to a preponderance of short wriggle bursts.Our study identifies specific ways in which trade-offs between predation risk and energetic costs could affect anti-predator behaviour.

捕食作用是一类强大的选择压力，可影响猎物种群与生态系统动态。识别捕食者及其对应的威胁等级，对猎物的应对行为至关重要。一旦侦测到捕食者，反捕食行为（anti-predatory responses）可提升猎物的生存概率。本研究以埃及伊蚊（Aedes aegypti）幼虫为实验材料，探究其对孔雀鱼（Poecilia reticulata）捕食威胁的行为响应。具体而言，我们分别测试了化学信号（chemical cues）单独存在、以及与物理信号（physical cues）联合存在时，在诱发反捕食行为（anti-predatory behaviours）中的相对重要性。实验结果显示，当幼虫同时暴露于化学与物理信号时，其通过缩短自身扭动爆发时长的方式，表现出比仅暴露于化学信号时更强的响应。反捕食行为往往伴随相应的适配成本，我们推测个体承担此类成本的能力，会影响其对捕食风险的响应模式。为验证这一假设，我们在同一实验中对比了饱腹幼虫与饥饿幼虫的扭动模式。结果发现，在捕食风险存在的条件下，饥饿幼虫较饱腹幼虫更愿意承担风险。为实验性验证“反捕食行为可提升猎物生存概率”这一前提假设，我们开展了后续实验。本次实验中，我们令饥饿的孔雀鱼在两类模拟幼虫的展示间进行选择——这两类幼虫的扭动爆发时长分别对应前期实验中观测到的短、长两种模式。实验结果显示，孔雀鱼优先攻击扭动爆发时长较长的幼虫，这证明了幼虫通过转向以短扭动爆发为主的反捕食策略，确实具备生存优势。本研究阐明了捕食风险与能量成本间的权衡取舍（trade-offs）可通过特定路径影响反捕食行为的具体机制。