Data from: Evidence for the Predator Attraction Hypothesis in an amphibian predator-prey system

Many species possess damage-released chemical alarm cues that function in alerting nearby individuals to a predator attack. One hypothesis for the evolution and/or maintenance of such cues is the Predator Attraction Hypothesis, where predators, rather than prey, are the 'intended' recipients of these cues. If a predator attack attracts additional predators, these secondary predators might interfere with the predation event, providing the prey with a better chance to escape. In this study, we conducted two experiments to explore this hypothesis in an amphibian predator/prey system. In Experiment 1, we found that tiger salamanders (Ambystoma mavortium) showed a foraging attraction to chemical cues from wood frog (Lithobates sylvaticus) tadpoles. Salamanders that were experienced with tadpole prey, in particular, were strongly attracted to tadpole alarm cues. In Experiment 2, we observed experimental encounters between a tadpole and either one or two salamanders. The presence of the second predator caused salamanders to increase attack speed at the cost of decreased attack accuracy (i.e., increasing the probability that the tadpole would escape attacks). We also found that the mere presence of visual and chemical cues from a second predator did not affect this speed/accuracy trade-off but did cause enough of a distraction to increase tadpole survival. Thus, our findings are thus consistent with the Predator Attraction Hypothesis for the evolution and/or maintenance of alarm cues.

诸多生物均会释放损伤释放型化学警戒信号（damage-released chemical alarm cues），其功能是向附近同类预警捕食者的袭击。针对此类信号的演化与维持机制，学界提出了一种假说——捕食者吸引假说（Predator Attraction Hypothesis）：该假说认为此类信号的“预期接收者”为捕食者而非猎物。若某次捕食袭击吸引了其他捕食者，这些次级捕食者将干扰当前的捕食过程，从而为猎物创造更多逃生机会。本研究针对两栖类捕食者-猎物系统开展了两项实验，以探究该假说的合理性。实验1结果显示，老虎钝口螈（Ambystoma mavortium）会对林蛙（Lithobates sylvaticus）蝌蚪释放的化学信号产生觅食趋性；其中，此前有捕食蝌蚪经历的钝口螈，对蝌蚪的警戒信号表现出极强的趋性。实验2中，我们观测了单只钝口螈与蝌蚪，以及两只钝口螈与蝌蚪的实验互动场景。结果发现，当存在第二只捕食者时，钝口螈会提升攻击速度，但代价是攻击准确率下降（即蝌蚪逃脱攻击的概率升高）。此外我们还发现，仅通过视觉与化学信号感知到第二只捕食者的存在，并不会改变钝口螈的速度-准确率权衡关系，但足以产生足够的干扰效果，提升蝌蚪的存活率。综上，本研究结果与警戒信号演化及维持的捕食者吸引假说（Predator Attraction Hypothesis）相符。