Lindström L, Rowe C, Guilford T
Department of Biological and Environmental Science, University of Fyväskylä, Finland.
Proc Biol Sci. 2001 Jan 22;268(1463):159-62. doi: 10.1098/rspb.2000.1344.
Unpalatable insects frequently adopt multimodal signals to ward off predators, incorporating sounds and odours into their colourful displays. Pyrazine is an odour commonly used in insect warning displays, and has previously been shown to elicit unlearned biases against common warning colours, e.g. yellow and red in naive predators. We designed two experiments to test for similar effects of pyrazine on the conspicuousness of prey, perhaps the most ubiquitous aspect of aposematic coloration. In the first experiment, we offered predators (Gallus gallus domesticus) a choice between conspicuous crumbs and cryptic crumbs in the presence or absence of pyrazine. In the second experiment, we manipulated the birds' experience of conspicuous prey during an initial training phase. Only in the presence of pyrazine did birds show a bias against conspicuously coloured food, and this occurred whether or not they had previously experienced food that contrasted with the background. This emergent behaviour relied upon the visual and odorous signal components being presented together. These unlearned, yet hidden, responses against conspicuousness demonstrate that there are initial benefits to prey being conspicuous when the multimodal nature of warning signals is accounted for.
难吃的昆虫经常采用多模态信号来抵御捕食者，将声音和气味融入它们色彩斑斓的展示中。吡嗪是一种常用于昆虫警示展示的气味，此前已被证明会引发对常见警示颜色（如天真的捕食者眼中的黄色和红色）的先天性偏好。我们设计了两个实验来测试吡嗪对猎物显眼性的类似影响，显眼性可能是警戒色最普遍的一个方面。在第一个实验中，我们让捕食者（家鸡）在有或没有吡嗪的情况下，在显眼的碎屑和隐蔽的碎屑之间进行选择。在第二个实验中，我们在初始训练阶段操纵了鸟类对显眼猎物的体验。只有在有吡嗪的情况下，鸟类才会对颜色显眼的食物表现出偏好，无论它们之前是否体验过与背景形成对比的食物。这种新出现的行为依赖于视觉和气味信号成分同时呈现。这些针对显眼性的先天性但隐藏的反应表明，当考虑到警示信号的多模态性质时，猎物显眼会有初步的好处。
