Aposematic prey advertise their unprofitability with conspicuous warning signals that are often composed of multiple color patterns. Many species show intraspecific variation in these patterns even though selection is expected to favor invariable warning signals that enhance predator learning. However, if predators acquire avoidance to specific signal components, this might relax selection on other aposematic traits and explain variability. Here, we investigated this idea in the aposematic moth Amata nigriceps that has conspicuous black and orange coloration. The size of the orange spots in the wings is highly variable between individuals, whereas the number and width of orange abdominal stripes remains consistent. We produced artificial moths that varied in the proportion of orange in the wings or the presence of abdominal stripes. We presented these to a natural avian predator, the noisy miner (Manorina melanocephala), and recorded how different warning signal components influenced their attack decisions. When moth models had orange stripes on the abdomen, birds did not discriminate between different wing signals. However, when the stripes on the abdomen were removed, birds chose the model with smaller wing spots. In addition, we found that birds were more likely to attack moths with a smaller number of abdominal stripes. Together, our results suggest that bird predators primarily pay attention to the abdominal stripes of A. nigriceps, and this could relax selection on wing coloration. Our study highlights the importance of considering individual warning signal components if we are to understand how predation shapes selection on prey warning coloration.

中文翻译：

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警戒蛾中多分量警告信号的捕食者选择

具有警戒性的猎物会通过通常由多种颜色图案组成的明显警告信号来宣传它们的无利可图。许多物种在这些模式中表现出种内变异，尽管选择预计有利于增强捕食者学习的不变的警告信号。然而，如果捕食者能够回避特定的信号成分，这可能会放松对其他警戒特征的选择并解释变异性。在这里，我们在具有明显的黑色和橙色颜色的警戒蛾黑头蛾（Amata nigriceps）中研究了这个想法。翅膀上橙色斑点的大小因个体而异，而腹部橙色条纹的数量和宽度保持一致。我们生产了人造飞蛾，其翅膀中橙色的比例或腹部条纹的存在各不相同。我们将这些信息展示给鸟类的自然捕食者——吵闹的矿工（Manorina melanocephala），并记录了不同的警告信号成分如何影响它们的攻击决策。当飞蛾模型腹部有橙色条纹时，鸟类无法区分不同的翅膀信号。然而，当腹部的条纹被去除后，鸟类选择了翼斑较小的模型。此外，我们发现鸟类更有可能攻击腹部条纹数量较少的飞蛾。总之，我们的结果表明鸟类捕食者主要关注黑头肌的腹部条纹，这可能会放松对翅膀颜色的选择。如果我们要了解捕食如何影响猎物警告颜色的选择，我们的研究强调了考虑个体警告信号成分的重要性。