Camouflage through colour change: mechanisms, adaptive value and ecological significance

Abstract

Animals from a wide range of taxonomic groups are capable of colour change, of which camouflage is one of the main functions. A considerable amount of past work on this subject has investigated species capable of extremely rapid colour change (in seconds). However, relatively slow colour change (over hours, days, weeks and months), as well as changes arising via developmental plasticity are probably more common than rapid changes, yet less studied. We discuss three key areas of colour change and camouflage. First, we review the mechanisms underpinning colour change and developmental plasticity for camouflage, including cellular processes, visual feedback, hormonal control and dietary factors. Second, we discuss the adaptive value of colour change for camouflage, including the use of different camouflage types. Third, we discuss the evolutionary–ecological implications of colour change for concealment, including what it can tell us about intraspecific colour diversity, morph-specific strategies, and matching to different environments and microhabitats. Throughout, we discuss key unresolved questions and present directions for future work, and highlight how colour change facilitates camouflage among habitats and arises when animals are faced with environmental changes occurring over a range of spatial and temporal scales.This article is part of the themed issue ‘Animal coloration: production, perception, function and application’.

Improved camouflage through ontogenetic colour change confers reduced detection risk in shore crabs

“…Our results also showed that the crabs developed more uniform patterning (see also Figure S2). It is not well known what maintains the high colour variation in juvenile crabs, but it may be related to the need to match variable background habitats at spatial scales (Nokelainen, Hubbard et al, ) that are relevant when individuals are small, and/or breaking predator search image formation (Bond & Kamil, ; Duarte et al, ; Karpestam et al, ; Punzalan et al, ). It is plausible that juvenile crabs may also rely on other types of camouflage, such as disruptive coloration (Todd et al, ), and this may be habitat‐specific, with crabs from rock pools favouring disruption and crabs from mudflats tending towards background matching.…”

“…The efficacy of camouflage is linked to the similarity of individuals with features of the visual environment (Troscianko, Wilson‐Aggarwal, Spottiswoode, & Stevens, ), and therefore, generally a given phenotype should be effective in hiding individuals in some environments but not in others (Ruxton et al, ; Stevens & Merilaita, ). Importantly, camouflage is often not static because many animals can change appearance over time during their life span, either through reversible plastic changes or via ontogenetic changes (Duarte, Flores, & Stevens, ; Stuart‐Fox & Moussalli, ). Yet, the mechanisms and implications of ontogenetic colour change for survival remain significantly unexplored.…”

“…Similar changes for camouflage tuning over days and weeks occur both within and between moults in other groups, such as grasshoppers (Burtt, ; Edelaar, Baños‐Villalba, Escudero, & Rodríguez‐Bernal, ; Peralta‐Rincon, Escudero, & Edelaar, ) and caterpillars (Eacock et al, ). Not only can individuals change their coloration over multiple time‐scales to facilitate camouflage, but many also undergo changes in appearance as a result of ontogeny (Duarte et al, ; Iampietro, ; Jensen & Egnotovich, ; Reid, Abello, Kaiser, & Warman, ; Stevens, ; Styrishave, Rewitz, & Andersen, ; Todd, Qiu, & Chong, ). For example, racer snakes become more uniform in coloration with age, a change that seems to be linked to behaviour and anti‐predator strategies (Creer, ).…”

The key role of behaviour in animal camouflage

“…Indirect evidence of microhabitat selection for camouflage also exists from field studies of freshwater turtles (Xiao et al, ). Beyond this, many crabs and other crustaceans show size‐/age‐dependent shifts in habitat use that correlate with changes in appearance (usually through ontogeny), and one potential explanation is that this is related to differences in predation risk and camouflage in different habitats (Todd, Qiu & Chong, ; Duarte et al, ).…”

Evolution of ontogenic change in color defenses of swallowtail butterflies

“…Prey species may also reduce the risk of predation from visually hunting predators using color defense strategies such as masquerade, crypsis, and aposematism (Booth, ; Caro, Sherratt, & Stevens, ; Cuthill et al., ; Higginson & Ruxton, ; Lichter‐Marck, Wylde, Aaron, Oliver, & Singer, ; Skelhorn, Rowland, Speed, & Ruxton, ; Speed, ). Masquerading prey resemble some inedible objects (at times, objects aversive to their predators, such as bird droppings) in their natural environment and are misidentified by predators, whereas cryptic prey avoid detection by matching the color and pattern of their body with those of the background (Duarte, Flores, & Stevens, ). Aposematic species, on the other hand, are usually chemically defended and therefore are distasteful and unprofitable and advertise their unpalatability through warning coloration to predators that learn to avoid harmful prey (Mappes, Marples, & Endler, ; Mukherjee & Heithaus, ; Stevens & Ruxton, ).…”