Disruptive coloration and background pattern matching

Abstract

Effective camouflage renders a target indistinguishable from irrelevant background objects. Two interrelated but logically distinct mechanisms for this are background pattern matching (crypsis) and disruptive coloration: in the former, the animal's colours are a random sample of the background; in the latter, bold contrasting colours on the animal's periphery break up its outline. The latter has long been proposed as an explanation for some apparently conspicuous coloration in animals, and is standard textbook material. Surprisingly, only one quantitative test of the theory exists, and one experimental test of its effectiveness against non-human predators. Here we test two key predictions: that patterns on the body's outline should be particularly effective in promoting concealment and that highly contrasting colours should enhance this disruptive effect. Artificial moth-like targets were exposed to bird predation in the field, with the experimental colour patterns on the 'wings' and a dead mealworm as the edible 'body'. Survival analysis supported the predictions, indicating that disruptive coloration is an effective means of camouflage, above and beyond background pattern matching.

Empirical tests of the role of disruptive coloration in reducing detectability

“…Other species have evolved a close resemblance to non-random yet inedible elements of their environment, such as leaves or rocks (Allen & Cooper 1985). Intriguingly, many camouflaged prey (including species of mollusc, crustacean, insect, snake, fish, bird and mammal) also exhibit highcontrast markings ('disruptive patterns';Thayer 1909;Cott 1940;Silberglied et al 1980;Merilaita 1998;Behrens 2002;Cuthill et al 2005Cuthill et al , 2006Sherratt et al 2005). Following Thayer (1909) and Cott (1940), these markings are thought to create false boundaries and/or obscure existing ones, thereby rendering detection of characteristic shapes more difficult.…”

“…Yet despite its widespread application, it is only recently that ecologists and evolutionary biologists have begun to test the effectiveness of disruptive coloration in the field, and to design experiments to distinguish between the benefits of background matching and disruptive coloration per se (Cuthill et al 2005;Merilaita & Lind 2005;Schaefer & Stobbe 2006;. In an influential recent paper, Cuthill et al (2005) pinned artificial mothlike prey, baited with mealworms, onto oak trees and evaluated their 'survivorship' over 24 h. In their main experiment, five different types of artificial moth were pinned out. Three of these moth types were brown and black, with the two colours and proportions chosen to match the colours of oak when printed onto triangular card (representing the moth's 'wings').…”

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

“…2005, 2006; Merilaita and Lind 2005; Schaefer and Stobbe 2006; Stevens et al. 2006; Stobbe and Schaefer 2008) and human predators (Fraser et al.…”

“…One disruptive coloration pattern that has been demonstrated to have a camouflage effect (e.g., Cuthill et al. 2005, 2006; Merilaita and Lind 2005; Fraser et al. 2007) is the “disruptive marginal pattern,” in which the disruptive markings touch the outline of the prey's body (Cott 1940; Stevens and Merilaita 2009b).…”

“…Disruptive marginal patterns are effective even when some of the pattern elements do not visually match adjacent parts of the background (Cuthill et al. 2005; Schaefer and Stobbe 2006; Stevens et al. 2006; but see Hegna and Mappes 2014).…”