Costs of colour change in fish: food intake and behavioural decisions

Abstract

SUMMARYMany animals, particularly reptiles, amphibians, fish and cephalopods, have the ability to change their body colour, for functions including thermoregulation, signalling and predator avoidance. Many fish plastically darken their body colouration in response to dark visual backgrounds, and this functions to reduce predation risk. Here, we tested the hypotheses that colour change in fish (1) carries with it an energetic cost and (2) affects subsequent shoal and habitat choice decisions. We demonstrate that guppies (Poecilia reticulata) change colour in response to dark and light visual backgrounds, and that doing so carries an energetic cost in terms of food consumption. By increasing food intake, however, guppies are able to maintain growth rates and meet the energetic costs of changing colour. Following colour change, fish preferentially choose habitats and shoals that match their own body colouration, and maximise crypsis, thus avoiding the need for further colour change but also potentially paying an opportunity cost associated with restriction to particular habitats and social associates. Thus, colour change to match the background is complemented by behavioural strategies, which should act to maximise fitness in variable environments.

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

“…Therefore, metabolic costs and other constraints associated with changing colour and maintaining chromatophore state may be important. One study has at least demonstrated that when guppy fish ( Poecilia reticulata ) are induced to change colour by altering the background, individuals increase their food consumption levels [21]. The implication is that increased food consumption occurs to offset the energetic costs of changing colour.…”

Comparing the consequences of natural selection, adaptive phenotypic plasticity, and matching habitat choice for phenotype–environment matching, population genetic structure, and reproductive isolation in meta‐populations

“…Such “matching habitat choice” thus allows individuals to be an agent instead of a target of selection and thereby exerts a distinct evolutionary force that can lead to adaptive evolution, even in the absence of natural selection (Bolnick & Otto, ; Edelaar & Bolnick, ). Empirical evidence for matching habitat choice is still limited, yet, some studies have shown that, for example, different phenotypes disperse and settle preferentially in habitats where they are more camouflaged (Dreiss et al., ; Gillis, ; Karpestam, Wennersten, & Forsman, ; Rodgers, Gladman, Corless, & Morrell, ) or more physiologically adapted (Bestion, Clobert, & Cote, ; Jacob et al., ).…”

Coral reef flounders,Bothus lunatus, choose substrates on which they can achieve camouflage with their limited body pattern repertoire

“…flounders, soles) and other bottom dwellers prefer to settle on sands or painted tank areas with background coloration and patterning similar to their own (Sumner, 1911(Sumner, , 1935Mast, 1914;Hewer, 1930;Fairchild & Howell, 2004;Ryer et al, 2008). Freshwater guppies and least killifish also prefer certain backgrounds (Kjernsmo & Merilaita, 2012;Rodgers et al, 2013). Among terrestrial animals, moths show a preference for backgrounds with colours similar to their own (Kettlewell & Conn, 1977;Steward, 1977;Endler, 1984) and they position their bodies to maximize crypsis (Webster et al, 2009;Kang et al, 2012).…”