Abstract
Defended prey often use distinctive, conspicuous, colours to advertise their unprofitability to potential predators (aposematism). These warning signals are frequently made up of salient, high contrast, stripes which have been hypothesized to increase the speed and accuracy of predator avoidance learning. Limitations in predator visual acuity, however, mean that these patterns cannot be resolved when viewed from a distance, and adjacent patches of colour will blend together (pattern blending). We investigated how saliency changes at different viewing distances in the toxic and brightly coloured cinnabar moth caterpillar (Tyria jacobaeae). We found that although the caterpillars' orange-and-black stripes are highly salient at close range, when viewed from a distance the colours blend together to match closely those of the background. Cinnabar caterpillars therefore produce a distance-dependent signal combining salient aposematism with targeted background matching camouflage, without necessarily compromising the size or saturation of their aposematic signal.
Highlights
Aposematic coloration signals directly to potential predators, warning that attempted predation is likely to be unprofitable [1,2]
UV photography revealed minimal UV reflectance from the caterpillar and the ragwort stem, there was high UV reflectance from the ragwort flowers’ outer petals. This negligible UV reflectance from the stem allowed the tetrachromatic vision of a passerine bird to be modelled from standard, but calibrated, RGB photography
It has been hypothesized that the orange-and-black stripes of the cinnabar caterpillar may provide both aposematism and camouflage [34]
Summary
Aposematic (warning) coloration signals directly to potential predators, warning that attempted predation is likely to be unprofitable [1,2]. Aposematic patterns frequently contain bright colours and high contrast patterning, which have been linked to. 10 mm greater speed and accuracy of predator avoidance learning, and have been hypothesized to increase the saliency of signals across heterogeneous backgrounds [2,3,4]
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