Coloration mediates the relationship between an organism and its environment in important ways, including social signaling, antipredator defenses, parasitic exploitation, thermoregulation, and protection from ultraviolet light, microbes, and abrasion. Methodological breakthroughs are accelerating knowledge of the processes underlying both the production of animal coloration and its perception, experiments are advancing understanding of mechanism and function, and measurements of color collected noninvasively and at a global scale are opening windows to evolutionary dynamics more generally. Here we provide a roadmap of these advances and identify hitherto unrecognized challenges for this multi- and interdisciplinary field.

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Masquerade describes the resemblance of an organism to an inedible object and is hypothesized to facilitate misidentification of that organism by its predators or its prey. To date, there has been no empirical demonstration of the benefits of masquerade. Here, we show that two species of caterpillar obtain protection from an avian predator by being misidentified as twigs. By manipulating predators' previous experience of the putative model but keeping their exposure to the masquerader the same, we determined that predators misidentify masquerading prey as their models, rather than simply failing to detect them.

BackgroundQuantifying the conspicuousness of objects against particular backgrounds is key to understanding the evolution and adaptive value of animal coloration, and in designing effective camouflage. Quantifying detectability can reveal how colour patterns affect survival, how animals’ appearances influence habitat preferences, and how receiver visual systems work. Advances in calibrated digital imaging are enabling the capture of objective visual information, but it remains unclear which methods are best for measuring detectability. Numerous descriptions and models of appearance have been used to infer the detectability of animals, but these models are rarely empirically validated or directly compared to one another. We compared the performance of human ‘predators’ to a bank of contemporary methods for quantifying the appearance of camouflaged prey. Background matching was assessed using several established methods, including sophisticated feature-based pattern analysis, granularity approaches and a range of luminance and contrast difference measures. Disruptive coloration is a further camouflage strategy where high contrast patterns disrupt they prey’s tell-tale outline, making it more difficult to detect. Disruptive camouflage has been studied intensely over the past decade, yet defining and measuring it have proven far more problematic. We assessed how well existing disruptive coloration measures predicted capture times. Additionally, we developed a new method for measuring edge disruption based on an understanding of sensory processing and the way in which false edges are thought to interfere with animal outlines.ResultsOur novel measure of disruptive coloration was the best predictor of capture times overall, highlighting the importance of false edges in concealment over and above pattern or luminance matching.ConclusionsThe efficacy of our new method for measuring disruptive camouflage together with its biological plausibility and computational efficiency represents a substantial advance in our understanding of the measurement, mechanism and definition of disruptive camouflage. Our study also provides the first test of the efficacy of many established methods for quantifying how conspicuous animals are against particular backgrounds. The validation of these methods opens up new lines of investigation surrounding the form and function of different types of camouflage, and may apply more broadly to the evolution of any visual signal.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0854-2) contains supplementary material, which is available to authorized users.

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Many organisms appear to mimic inanimate objects such as twigs, leaves, stones, and bird droppings. Such adaptations are considered to have evolved because their bearers are misidentified as either inedible objects by their predators, or as innocuous objects by their prey. In the past, this phenomenon has been classified by some as Batesian mimicry and by others as crypsis, but now is considered to be conceptually different from both, and has been termed 'masquerade'. Despite the debate over how to classify masquerade, this phenomenon has received little attention from evolutionary biologists. Here, we discuss the limited empirical evidence supporting the idea that masquerade functions to cause misidentification of organisms, provide a testable definition of masquerade, and suggest how masquerade evolved and under what ecological conditions. (C) 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99, 1-8

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Toxic prey advertise their unprofitability to predators via conspicuous aposematic coloration [1]. It is widely accepted that avoidance learning by naive predators is fundamental in generating selection for aposematism [2, 3] and mimicry [4, 5] (where species share the same aposematic coloration), and consequently this cognitive process underpins current evolutionary theory [5, 6]. However, this is an oversimplistic view of predator cognition and decision making. We show that predators that have learned to avoid chemically defended prey continue to attack defended individuals at levels determined by their current toxin burden. European starlings learned to discriminate between sequentially presented defended and undefended mealworms with different color signals. Once birds had learned to avoid the defended prey at a stable asymptotic level, we experimentally increased their toxin burdens, which reduced the number of defended prey that they ingested in the subsequent trial. This was due to the birds making strategic decisions to ingest defended prey on the basis of their visual signals. Birds are clearly able to learn about the nutritional benefits and defensive costs of eating defended prey, and they regulate their intake according to their current physiological state. This raises new perspectives on the evolution of aposematism, mimicry, and defense chemistry.