Collateral damage or a shadow of safety? The effects of signaling heterospecific neighbors on the risks of parasitism and predation

Although males often display from mixed-species aggregations, the influence of nearby heterospecifics on risks associated with sexual signaling has not been previously examined. We tested whether predation and parasitism risks depend on proximity to heterospecific signalers. Using field playback experiments with calls of two species that often display from the same ponds, túngara frogs and hourglass treefrogs, we tested two hypotheses: (1) Calling near heterospecific signalers attractive to eavesdroppers results in increased attention from predatory bats and parasitic midges (Collateral Damage hypothesis); or (2) Calling near heterospecific signalers reduces an individual’s predation and parasitism risks, as eavesdroppers are drawn to the heterospecifics (Shadow of Safety hypothesis). Bat visitation was not affected by calling neighbors. The number of frog-biting midges attracted to hourglass treefrog calls, however, rose threefold when played near túngara calls, supporting the collater...尽管雄性个体常于混合物种种群中开展求偶炫耀，但此前尚未有研究探讨近距异种个体对性信号相关风险的影响。本研究旨在探究捕食与寄生风险是否取决于与异种信号发送者的空间距离。我们针对常同域栖息于同一繁殖池塘的两种蛙类——泡蟾（túngara frogs）与沙漏树蛙（hourglass treefrogs），开展野外回放发声实验，以此验证两项假说：（1）当在易被信号窃听者识别的异种信号发送者附近鸣叫时，会招致捕食性蝙蝠与寄生蠓的更多关注，此即"附带伤害假说（Collateral Damage hypothesis）"；（2）当在异种信号发送者附近鸣叫时，个体的捕食与寄生风险会降低，因为信号窃听者会被异种个体吸引，此即"安全阴影假说（Shadow of Safety hypothesis）"。实验结果显示，蝙蝠的到访频次并未受鸣叫邻居的影响。不过，当沙漏树蛙的鸣唱回放与泡蟾鸣唱同步播放时，吸引到的蛙寄生蠓数量增加了三倍，这一结果支持了附带伤害假说（原文未完整收尾）。