Selection for cryptic coloration in a visually heterogeneous habitat

Abstract

We studied selection by predators for cryptic prey coloration in a visually heterogeneous habitat that consists of two microhabitats. It has been suggested that the probability of escaping detection in such habitats might be optimized by maximizing crypsis in one of the microhabitats. However, a recent model indicates that a coloration that compromises the requirements of di¡erent microhabitats might sometimes be the optimal solution. To experimentally study these hypotheses, we allowed great tits (Parus major L.) to search for arti¢cial prey items in two di¡erent microhabitats (background boards): small patterned and large patterned. On each board there was one prey item that was either small-patterned, large-patterned or medium-patterned and thus compromised. Search time was used as the measure of crypsis and was on average longer on the large-patterned than on the small-patterned background. On the small-patterned background, the small-patterned prey was more cryptic than the compromised prey, which was in turn more cryptic than the large-patterned prey. On the large-patterned background, the small-patterned prey was least cryptic, but the compromised prey did not di¡er signi¢cantly from the large-patterned prey. The compromised coloration had lower predation risk than the matching colorations. This indicates that in some conditions a compromised coloration might be the best strategy for the prey and has important implications for the study of animal coloration.

Visual Background Complexity Facilitates the Evolution of Camouflage

“…Dukas 1998). This idea is supported by a previous predation experiment in which the risk of detection did not vary simply in accordance with background matching of the prey (Merilaita et al 2001). …”

“…Maximization of such effect is not always in accordance with maximization of background matching of the geometry and colors of the coloration (Merilaita 1998). Second, in visually heterogeneous habitats the optimal coloration is sometimes coloration that is a compromise between the requirements of several microhabitats instead of matching any one microhabitat (Norris and Lowe 1964;Shreeve 1990;Merilaita et al 1999Merilaita et al , 2001). Such compromise is more likely to be favored if the requirement for background matching is not stringent (Merilaita et al 1999).…”

Camouflage and Perceptual Organization in the Animal Kingdom

“…As a result, a camouflaged animal may be better concealed in more complex habitats independent of its match to the background (Merilaita et al 2001;Merilaita 2003;Dimitrova & Merilaita 2010). In line with this, there is recent evidence for animals choosing backgrounds that are not merely a good match to their own patterns, but are more visually complex (Kjernsmo & Merilaita 2012).…”

“…Endler (1978Endler ( , 1984Endler ( , 1991 proposed that crypsis should be defined as coloration that represents a random sample of the background at the place and time where predation risk is highest. Others have argued that a random sample is not necessarily optimal (Merilaita et al 1999(Merilaita et al , 2001Ruxton et al 2004) supported by experiments showing that not all random samples are equally concealed (Merilaita et al 1999). If the background is heterogeneous and a single sample must be chosen (i.e.…”

Feeding visit time of fruit-eating birds in Cerrado plants: revisiting the predation risk model

“…For color comparisons, we classified each bird species as cryptic or conspicuous. Crypsis is a background specific adaptation, so that increased crypsis in one microhabitat is expected to decrease crypsis in another one (MERILAITA et al 2001). Hence, we classified as cryptic only those birds in which the colors of the back, front and belly were similar to plant colors, that is, brown, gray, and green-feathered birds.…”