Animal camouflage: current issues and new perspectives

Abstract

The study of camouflage has a long history in biology, and the numerous ways of concealment and disguise found in the animal kingdom provided Darwin and Wallace with important examples for illustrating and defending their ideas of natural selection and adaptation. Thus, various forms of camouflage have become classical examples of evolution. In a broader sense, camouflage has been adopted by humans, most notably by the military and hunters, but it has also influenced other parts of society, for example, arts, popular culture and design.Animals use camouflage to make detection or recognition more difficult, with most examples associated with visual camouflage involving body coloration. However, in addition to coloration, camouflage may make use of morphological structures or material found in the environment, and may even act against senses other than vision (Ruxton 2009). In nature, some of the most striking examples of adaptation can be found with respect to avoiding being detected or recognized, with the strategies employed diverse, and sometimes extraordinary. Such strategies can include using markings to match the colour and pattern of the background, as in various moths (e.g. Kettlewell 1955), and to break up the appearance of the body, as in some marine isopods (Merilaita 1998). Camouflage is a technique especially useful if the animal can change colour to match the background on which it is found, such as can some cephalopods (Hanlon & Messenger 1988) and chameleons (Stuart-Fox et al. 2008). Further remarkable examples include insects bearing an uncanny resemblance to bird droppings (Hebert 1974) or fish resembling fallen leaves on a stream bed (Sazima et al. 2006), to even making the body effectively transparent, as occurs in a range of, in particular, aquatic species (Johnsen 2001;Carvalho et al. 2006). Examples such as

Camouflage and Perceptual Organization in the Animal Kingdom

“…A naive view is that camouflage 'matches the background', but the simplicity of the concept has proved deceptive and led to controversies about definitions up to the present day (for instance Stevens & Merilaita's 2009 arguments about cryptic camouflage). An exact physical match, such that pattern on the animal and the substrate against which it is viewed are perceptually identical, is possible only with a uniform background; if only because differences in pattern phase at the boundary between object and background, or 3D cues from shadowing on its surface, are almost inevitable.…”

“…Cott greatly refined Thayer's original ideas, and he produced a battery of illustrations from across the animal kingdom to explain how disruption could work and plausibly illustrate their action in nature (Figure 2A). However, as recent researchers have realised, the term 'disruptive coloration' actually comprises several mechanisms, and some of those discussed by Thayer and Cott as disruptive are better classified differently (Stevens & Merilaita 2009). We discuss these in turn.…”

“…Camouflage works by defeating figure-ground segregation, whereas patterns that disguise the animal as a commonplace object or lead to misclassification are known as masquerade and mimicry (Endler 1981;Ruxton et al 2004b; but see also Stevens & Merilaita 2009 for discussion these terms). Mimicry patterns, which are often conspicuous, work by similarity to a different animal, typically one that is avoided by the predator, whereas in masquerade the animal resembles a commonplace but valueless object, such as a birddropping or plant thorn.…”

Squeezing out the last egg—annual fish increase reproductive efforts in response to a predation threat

“…For instance, behavioral responses such as hiding, flashing of colored body parts, or gregarious behavior have all been shown to enhance prey survival rates (Daly, Behrends, Wilson, & Jacobs, 1992; Edmunds, 1974; Sih, 1987; Stevens, 2005). Morphological features include for instance camouflage, aposematic coloration, Batesian mimicry, and protective spines or plates (Edmunds, 1974; Hoogland, Morris, & Tinbergen, 1956; Skelhorn, Rowland, & Ruxton, 2010; Stevens & Merilaita, 2009). In terms of life history responses, predation pressure has been shown to induce shifts in age at maturity, fecundity, and growth (Reznick, Butler Iv, & Rodd, 2001; Stoks, Govaert, Pauwels, Jansen, & De Meester, 2016) to increase prey fitness.…”

Warning coloration can be disruptive: aposematic marginal wing patterning in the wood tiger moth

“…1981) because adjacent markings in disruptive patterns are likely to be more contrasting; therefore, at least some of them may contrast with background colors. However, clear evidence in support of this hypothesis has not yet been presented (Stevens and Merilaita 2009a; Bohlin et al. 2012; Hegna and Mappes 2014).…”