The key role of behaviour in animal camouflage

Abstract

Animal camouflage represents one of the most important ways of preventing (or facilitating) predation. It attracted the attention of the earliest evolutionary biologists, and today remains a focus of investigation in areas ranging from evolutionary ecology, animal decision-making, optimal strategies, visual psychology, computer science, to materials science. Most work focuses on the role of animal morphology per se, and its interactions with the background in affecting detection and recognition. However, the behaviour of organisms is likely to be crucial in affecting camouflage too, through background choice, body orientation and positioning; and strategies of camouflage that require movement. A wealth of potential mechanisms may affect such behaviours, from imprinting and self-assessment to genetics, and operate at several levels (species, morph, and individual). Over many years there have been numerous studies investigating the role of behaviour in camouflage, but to date, no effort to synthesise these studies and ideas into a coherent framework. Here, we review key work on behaviour and camouflage, highlight the mechanisms involved and implications of behaviour, discuss the importance of this in a changing world, and offer suggestions for addressing the many important gaps in our understanding of this subject.

Keywords: behaviour; camouflage; crypsis; decision-making; learning; movement; vision.

Figure 1

Examples of animals using background choice behaviour for camouflage. (A) Kallima leaf‐mimicking butterfly that Wallace noted tends to rest on dead vegetation. (B) Ghost crab (Ocypode sp.) which can change colour and selects sand backgrounds that match its individual appearance. (C) Bronze‐winged courser (Rhinoptilus chalcopterus) parents select nesting backgrounds that better match egg appearance. (D) Fiery‐necked nightjars (Caprimulgus pectoralis) select nesting backgrounds to match adult plumage. (E) Aegean wall lizards (Podarcis erhardii) choose to sit on backgrounds that match their own appearance better, especially for females and on islands with higher predation rates. (F) Many moths select backgrounds and body positions/orientations to match key features of the background, such as tree bark. (G) Some animals like caterpillars hold their bodies in postures to resemble the shape of twigs and bird droppings. (H) Grasshoppers have been shown to sit in positions that better align themselves with the background, reducing detection.

Figure 2

Animals use behaviour in multiple ways to facilitate camouflage. (A) Some insects that mimic twigs or other objects sway in a manner to match background vegetation movement. Species unknown. (B) Animals like this eyed‐hawk moth caterpillar (Smerinthus ocellata) orientate their body to facilitate the reduction of shadows. (C) Various species, such as this long‐legged spider crab (Macropodia rostrata) attach material from the environment to their body in decorating behaviour. (D) It has been suggested that the appearance of striped animals, potentially zebra (Equus sp.), may cause predators to misdirect attacks due to motion dazzle. (E, F) Some species, such as Kittlitz's plovers (Charadrius pecuarius) modify the nesting environment to hide or camouflage their eggs (E, natural clutch; F, uncovered).