In dense mating aggregations, such as leks and choruses, acoustic signals produced by competing male conspecifics often overlap in time. When signals overlap at a fine temporal scale the ability of females to discriminate between individual signals is reduced. Yet, despite this cost, males of some species deliberately overlap their signals with those of conspecifics, synchronizing signal production in the chorus. Here, we investigate two hypotheses of synchronized mating signals in a Japanese treefrog (Buergeria japonica): (1) increased female attraction to the chorus (the beacon effect hypothesis) and (2) reduced attraction of eavesdropping predators (the eavesdropper avoidance hypothesis). Our results from playback experiments on female frogs and eavesdropping micropredators (midges and mosquitoes) support both hypotheses. Signal transmission and female phonotaxis experiments suggest that away from the chorus, synchronized calls are more attractive to females than unsynchronized calls. At the chorus, however, eavesdroppers are less attracted to calls that closely follow an initial call, while female attraction to individual signals is not affected. Therefore, synchronized signalling likely benefits male B. japonica by both increasing attraction of females to the chorus and reducing eavesdropper attacks. These findings highlight how multiple selective pressures likely promoted the evolution and maintenance of this behaviour.

This article is part of the theme issue ‘Synchrony and rhythm interaction: from the brain to behavioural ecology’.

在密集的交配聚集体中，例如 leks 和 choruses，竞争雄性同种产生的声学信号通常在时间上重叠。当信号在精细的时间尺度上重叠时，女性区分单个信号的能力就会降低。然而，尽管付出了这样的代价，一些物种的雄性故意将它们的信号与同种的信号重叠，使合唱中的信号产生同步。在这里，我们研究了日本树蛙（Buergeria japonica ）中同步交配信号的两个假设。）：（1）增加女性对合唱的吸引力（信标效应假设）和（2）减少窃听捕食者的吸引力（窃听者回避假设）。我们对雌性青蛙和窃听小食肉动物（蠓和蚊子）的回放实验结果支持这两个假设。信号传输和女性发声实验表明，在合唱之外，同步呼叫比不同步呼叫更能吸引女性。然而，在合唱中，窃听者对紧随初始呼叫的呼叫的吸引力较小，而女性对单个信号的吸引力则不受影响。因此，同步信号可能有利于雄性B. japonica通过增加女性对合唱的吸引力和减少窃听者的攻击。这些发现强调了多重选择压力可能如何促进这种行为的演变和维持。

这篇文章是主题问题“同步和节奏交互：从大脑到行为生态学”的一部分。