Effect of leaf moisture on wolf spider communication

We examined the effect of wet vs. dry leaves on aspects of wolf spider communication and mating success. Results show that environmental moisture conditions can influence efficacy of spider communication, detection of predators, and ultimately mating success. Data include:
• Laser vibrometry recordings showing that both stridulation and percussive signals maintain significantly higher amplitude over distance on dry leaves than wet leaves.
• Male responses to chemical cues (courtship latency and display rate) declined after leaves with female silk became wet.
• In response to predatory bird calls (Blue Jays) transmitted through leaf surfaces, courting male spiders on dry leaves responded with anti-predator “freeze” behaviors more often and for longer duration than those on wet leaves, and took longer to resume courtship than on wet leaves.
• Males courted females on wet and dry leaves with equal frequency, but mating success was significantly greater on dry leaf litter. Interestingly, visual signals increased on wet leaves, suggesting compensatory behavior in response to moisture.

These findings are important because the mating season of many wolf spider species occurs in spring, when there are frequent rains, and when insectivorous birds are selectively provisioning nestlings with spiders. Consequently, increased seasonal rainfall owing to climate change may disproportionately impact the leaf litter microhabitat and change the transmission properties of leaf substrates used for communication by spiders and other invertebrates.

本研究探究了湿润与干燥叶片对狼蛛通讯行为及交配成功率的影响。研究结果显示，环境湿度条件可影响蜘蛛通讯的有效性、天敌探测能力，并最终作用于其交配成功率。本次研究的数据包括：
• 激光测振仪（Laser vibrometry）记录表明：相较于湿润叶片，干燥叶片上的摩擦发声（stridulation）与敲击信号（percussive signals）在远距离传播过程中可维持显著更高的振幅。
• 当附着有雌蛛蛛丝的叶片变湿润后，雄蛛对化学信号的响应（包括求偶潜伏期与展示频率）均出现下降。
• 在通过叶片表面传递捕食性鸟类（冠蓝鸦Blue Jays）的鸣叫声时，栖息于干燥叶片上的求偶雄蛛，其展现反捕食“僵住”行为的频率更高、持续时间更长，且相较于湿润叶片上的个体，恢复求偶行为所需的时间也更久。
• 雄蛛在湿润与干燥叶片上对雌蛛的求偶频率无显著差异，但干燥枯落物生境中的交配成功率显著更高。值得注意的是，湿润叶片上的视觉信号频次有所提升，提示蜘蛛会针对湿度变化产生补偿性行为。

本研究结果具有重要学术价值：多数狼蛛物种的交配季处于春季，此时降雨频发，且食虫鸟类正选择性地以蜘蛛为食喂养雏鸟。因此，气候变化引发的季节性降雨增加，可能会对枯落物微生境造成不成比例的影响，并改变蜘蛛及其他无脊椎动物用于通讯的叶片基质的信号传播特性。