Optimal background matching camouflage

Abstract

Background matching is the most familiar and widespread camouflage strategy: avoiding detection by having a similar colour and pattern to the background. Optimizing background matching is straightforward in a homogeneous environment, or when the habitat has very distinct sub-types and there is divergent selection leading to polymorphism. However, most backgrounds have continuous variation in colour and texture, so what is the best solution? Not all samples of the background are likely to be equally inconspicuous, and laboratory experiments on birds and humans support this view. Theory suggests that the most probable background sample (in the statistical sense), at the size of the prey, would, on average, be the most cryptic. We present an analysis, based on realistic assumptions about low-level vision, that estimates the distribution of background colours and visual textures, and predicts the best camouflage. We present data from a field experiment that tests and supports our predictions, using artificial moth-like targets under bird predation. Additionally, we present analogous data for humans, under tightly controlled viewing conditions, searching for targets on a computer screen. These data show that, in the absence of predator learning, the best single camouflage pattern for heterogeneous backgrounds is the most probable sample.

Camouflage

“…Michalis et al . (), in field experiments where both humans and avian predators searched for background‐matching artificial prey, showed that the best single camouflage pattern was that of the most likely background sample (where ‘likely’ was quantified using colour and texture modelling of the kind described earlier).…”

“…Michalis et al . () were investigating the situation of a variable, but single type of, background, and infrequent encounters by the predator relative to other prey types. They pointed out that, conversely, if predators learnt the characteristics of a specific pattern through repeated encounters, then negative frequency‐dependent selection would favour polymorphism.…”

Gray plumage color is more cryptic than brown in snowy landscapes in a resident color polymorphic bird

“…Maybe the most fundamental strategy to gain protection from predators is via camouflage, which makes prey difficult to detect from its background (Merilaita & Stevens, ). Efficacy of camouflage is always dependent on its visual background (Endler, ; Hughes, Liggins, & Stevens, ; Michalis, Scott‐Samuel, Gibson, & Cuthill, ). Spatial and temporal variation in visual environments (e.g., darkness of the background) can lead to the evolution of color polymorphisms, that is, the coexistence of genetically different color morphs within a population (Bond & Kamil, ; Cook, ; Fisher, ; Ford, ; Roulin, ).…”

Background matching, disruptive coloration, and differential use of microhabitats in two neotropical grasshoppers with sexual dichromatism

“…However, part of the human visible spectrum overlaps with the possible visible spectrum from other predators. Thus, mice use part of the visual human spectrum (green and red) to detect potential prays (Denman et al, ), and under certain conditions, birds and humans have shown similar performance in detection tasks (Dukas & Kamil, ; Michalis et al, ). Further studies on predation and escape behavior are needed to test the effectiveness of both coloration cryptic strategies that we suggest in this report.…”