Accuracy of background matching and prey detection: predation by blue tits indicates intense selection for highly matching prey colour pattern

Abstract

Summary 1.Although background matching decreases prey detectability, resemblance between camouflaged prey and their visual background is seldom perfect. This could be because even a moderate resemblance might provide sufficient protection, and additional adjustment of colour pattern might give little benefit. Alternatively, close resemblance to background may not be attained due to trade-offs or constraints. To understand selection on colour patterns of camouflaged prey and the existence of inaccurate background matching, it is necessary to investigate how detectability of a colour pattern varies with its resemblance to the background. 2. We trained wild-caught blue tits (Cyanistes caeruleus) to search for artificial prey. We manipulated the resemblance of the artificial prey items to the visual backgrounds. 3. For the first half of the twelve repeated prey presentations, we found a nonlinear relationship between resemblance and detectability such that for prey that had high background matching, a change in resemblance resulted in a larger change in detectability than an equal change in resemblance did for prey with lower background matching. However, for the second half of the presentations, this relationship was linear. Moreover, in a two-patch-type habitat, a prey pattern that was a compromise between the two different backgrounds did after few initial presentations equally well as the prey pattern that matched highly one of the backgrounds. 4. Our results indicate an intense selection for close matching in a single background. Yet, in the heterogeneous environment that consisted of two backgrounds, the compromise, which only loosely resembled either background, provided good protection. Therefore, we conclude that cryptic colour patterns that bear only a loose resemblance to a given background, and thus represent inaccurate background matching, may be adaptive outcomes.

The Role of Life-History and Ecology in the Evolution of Color Patterns in Australian Chrysomeline Beetles

“…Animal color patterns are rarely "matched" with their background, because habitats are usually heterogeneous, and therefore provide backgrounds that vary visually in time and space (Merilaita and Dimitrova, 2014). Nevertheless, background matching is especially important for individuals that are exposed while feeding (Pellissier et al, 2011;Kjernsmo and Merilaita, 2012), since the risk of predation can increase by up to a 100-fold (Bernays, 1997).…”

Spatial and temporal variation in prey color patterns for background matching across a continuous heterogeneous environment

“…Many studies on background matching have looked at disjunct habitat patches (Hughes et al, 2019;Merilaita, 2003;Merilaita & Dimitrova, 2014;Merilaita et al, 2001Merilaita et al, , 1999, but few have quantified variation in background matching along a continuum of a habitat's visual characteristics. In particular, it is unclear how the need for background matching affects the color patterns of a population living in an area that varies continuously from one extreme habitat (e.g., open area) to another extreme (e.g., highly vegetated area).…”

Crypsis Decreases with Elevation in a Lizard

“…Visual crypsis by colour matching has long received considerable attention [7]. Experimental evidence supports that predators prey more frequently on conspicuous prey rather than on cryptic prey, favouring those whose colours better match the background [11][12][13][14][15][16][17][18][19]. Moreover, some field studies evidence that prey survival improves with visual crypsis [20][21][22].…”