Aposematism: balancing salience and camouflage

Aposematic signals are often characterized by high conspicuousness. Larger and brighter signals reinforce avoidance learning, distinguish defended from palatable prey and are more easily memorized by predators. Conspicuous signalling, however, has costs: encounter rates with naive, specialized or nu...

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Bibliographic Details
Published in:Biology letters (2005) 2016-08, Vol.12 (8), p.20160335-20160335
Main Authors: Barnett, James B., Scott-Samuel, Nicholas E., Cuthill, Innes C.
Format: Article
Language:English
Subjects:
Animal Behaviour
Animals
Aposematism
Avoidance Learning
Biological Evolution
Biological Mimicry
Birds
Camouflage
Color
Defensive Coloration
Honest Signalling
Predatory Behavior
Visual Signalling
Warning Signals
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Summary:Aposematic signals are often characterized by high conspicuousness. Larger and brighter signals reinforce avoidance learning, distinguish defended from palatable prey and are more easily memorized by predators. Conspicuous signalling, however, has costs: encounter rates with naive, specialized or nutritionally stressed predators are likely to increase. It has been suggested that intermediate levels of aposematic conspicuousness can evolve to balance deterrence and detectability, especially for moderately defended species. The effectiveness of such signals, however, has not yet been experimentally tested under field conditions. We used dough caterpillar-like baits to test whether reduced levels of aposematic conspicuousness can have survival benefits when predated by wild birds in natural conditions. Our results suggest that, when controlling for the number and intensity of internal contrast boundaries (stripes), a reduced-conspicuousness aposematic pattern can have a survival advantage over more conspicuous signals, as well as cryptic colours. Furthermore, we find a survival benefit from the addition of internal contrast for both high and low levels of conspicuousness. This adds ecological validity to evolutionary models of aposematic saliency and the evolution of honest signalling.
ISSN:1744-9561
1744-957X
DOI:10.1098/rsbl.2016.0335