Empirical tests of the role of disruptive coloration in reducing detectability

Abstract

Disruptive patterning is a potentially universal camouflage technique that is thought to enhance concealment by rendering the detection of body shapes more difficult. In a recent series of field experiments, artificial moths with markings that extended to the edges of their 'wings' survived at higher rates than moths with the same edge patterns inwardly displaced. While this result seemingly indicates a benefit to obscuring edges, it is possible that the higher density markings of the inwardly displaced patterns concomitantly reduced their extent of background matching. Likewise, it has been suggested that the mealworm baits placed on the artificial moths could have created differential contrasts with different moth patterns. To address these concerns, we conducted controlled trials in which human subjects searched for computer-generated moth images presented against images of oak trees. Moths with edge-extended disruptive markings survived at higher rates, and took longer to find, than all other moth types, whether presented sequentially or simultaneously. However, moths with no edge markings and reduced interior pattern density survived better than their high-density counterparts, indicating that background matching may have played a so-far unrecognized role in the earlier experiments. Our disruptively patterned nonbackground-matching moths also had the lowest overall survivorship, indicating that disruptive coloration alone may not provide significant protection from predators. Collectively, our results provide independent support for the survival value of disruptive markings and demonstrate that there are common features in human and avian perception of camouflage.

Camouflage and Perceptual Organization in the Animal Kingdom

“…This study showed that colour blocks that intersected the edge of the 'wing' reduced the rate of attacks on the models compared to otherwise similar controls with only internal patterning, or uniformly coloured. A computer-based experiment using the same sort of targets on pictures of tree bark replicated the results with humans (Fraser et al 2007), suggesting that the perceptual mechanisms being fooled are in common across birds and humans. Most plausible would be continuity of strong edges, suggesting a bounding contour.…”

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

“…2006; Stobbe and Schaefer 2008) and human predators (Fraser et al. 2007). 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.…”

“…However, some evidence indicates that the survival of individuals with disruptive color patterns characterized by extremely high contrast between adjacent color pattern elements (i.e., “maximum disruptive contrast”; Stevens and Merilaita 2009b) is worse than that of individuals with less contrasting patterns, because the contrast of the pattern elements with background elements is also high (Fraser et al. 2007; Stobbe and Schaefer 2008; Troscianko et al. 2013).…”

Birds build camouflaged nests

“…In background matching, the surface of an object is made inconspicuous by having the same coloration as its background (Stevens and Merilaita 2011). In disruptive coloration, distinctive markings, often composed of background-matching colors, are used to create the impression of false boundaries and edges in the object, breaking up its shape and making its outline less easily identifiable (Stevens et al 2006a, 2006b, Fraser et al 2007, Stevens and Merilaita 2011. In the present study, we are concerned primarily with background matching.…”