Complex sensory environments alter mate choice outcomes

Noise is a common problem in animal communication. We know little, however, about how animals communicate in noise using multimodal signals. Multimodal signals are hypothesized to be favoured by evolution because they increase the efficacy of detection/discrimination in noisy environments. We tested the hypothesis that female túngara frogs’ responses to attractive male advertisement calls are improved in noise when a visual cue is added. We tested this at two levels of decision complexity (two and three choices). In a two-choice test, the presence of noise did not reduce female preferences for attractive calls. The visual cue of a calling male, associated with an unattractive call, also did not reduce preference for attractive calls in the absence of noise. In the presence of noise, however, females were more likely to choose an unattractive call coupled with the visual cue. In three-choice tests, the presence of noise alone reduced female responses to attractive calls and this was not strongly affected by the presence or absence of visual cues. The responses in these experiments fail to support the multimodal signal efficacy hypothesis. Instead, the data suggest that audio-visual perception and cognitive processing, related to mate choice decisions, are dependent on the complexity of the sensory scene.

噪声是动物通讯领域普遍存在的干扰问题。然而，当前学界对动物如何借助多模态信号（multimodal signals）在噪声环境中完成通讯仍缺乏深入认知。多模态信号被演化所青睐的假说认为，其可提升噪声环境下信号的探测与识别效能。本研究针对该假说开展验证：当添加视觉线索时，华丽泡蟾（túngara frog）雌性个体对具有吸引力的雄性广告鸣唱的反应，可在噪声环境中得到改善。我们在两类决策复杂度水平（二选一与三选一任务）下开展了实验测试。在二选一任务中，噪声的存在并未降低雌性个体对优质鸣唱的偏好；在无噪声条件下，与无吸引力鸣唱绑定的鸣叫雄性视觉线索，同样未削弱雌性对优质鸣唱的偏好。但在噪声环境中，雌性个体更倾向于选择与视觉线索绑定的无吸引力鸣唱。在三选一任务中，仅噪声的存在便会降低雌性对优质鸣唱的反应，且这一效应不受视觉线索有无的显著影响。本实验所得结果并不支持多模态信号效能假说。与之相反，实验数据表明，与配偶选择决策相关的视听感知与认知加工过程，依赖于感官场景的复杂度。