Context-dependent coloration of prey and predator decision making in contrasting light environments

Abstract

A big question in behavioral ecology is what drives diversity of color signals. One possible explanation is that environmental conditions, such as light environment, may alter visual signaling of prey, which could affect predator decision-making. Here, we tested the context-dependent predator selection on prey coloration. In the first experiment, we tested detectability of artificial visual stimuli to blue tits (Cyanistes caeruleus) by manipulating stimulus luminance and chromatic context of the background. We expected the presence of the chromatic context to facilitate faster target detection. As expected, blue tits found targets on chromatic yellow background faster than on achromatic grey background whereas in the latter, targets were found with smaller contrast differences to the background. In the second experiment, we tested the effect of two light environments on the survival of aposematic, color polymorphic wood tiger moth (Arctia plantaginis). As luminance contrast should be more detectable than chromatic contrast in low light intensities, we expected birds, if they find the moths aversive, to avoid the white morph which is more conspicuous than the yellow morph in low light (and vice versa in bright light). Alternatively, birds may attack first moths that are more detectable. We found birds to attack yellow moths first in low light conditions, whereas white moths were attacked first more frequently in bright light conditions. Our results show that light environments affect predator foraging decisions, which may facilitate context-dependent selection on visual signals and diversity of prey phenotypes in the wild.

Exploring polymorphism in a palatable prey: predation risk and frequency dependence in relation to distinct levels of conspicuousness

“…Vision modeling and higher predation rate suggest that the white morph is indeed more conspicuous than the melanic morph. Achromatic contrast is known to provide a more reliable detection channel for a foraging bird in motion than chromatic contrast ( Nokelainen et al, 2022 ). The relatively low chromatic contrast of both morphs on the background is therefore unlikely to significantly change the relative conspicuousness of the morphs given their large differences in achromatic contrast ( Schaefer et al, 2006 ).…”

Predator selection on multicomponent warning signals in an aposematic moth

“…Another important factor that may influence warning signal detectability and predator responses is the light environment ( Rojas et al 2014 ). For example, birds choose to attack different color morphs of an aposematic wood tiger moth ( Arctia plantaginis ) depending on the light conditions ( Nokelainen et al 2022 ). Heterogeneity in the light environment and background might therefore influence the salience of the different warning signals elements, and their importance for predators could be context dependent.…”

Genetic colour variation visible for predators and conspecifics is concealed from humans in a polymorphic moth

“…Colour polymorphisms have several fitness consequences in the maintenance of genetic variation (Galarza et al, 2014; Gray & McKinnon, 2007; McKinnon & Pierotti, 2010). They can influence intraspecific variation in mating cues (Merrill et al, 2012; Nokelainen et al, 2012), fitness of colour morphs in different light environments due to increased predation risk (Nokelainen et al, 2014, 2021; Rojas et al, 2014) and divergence in thermoregulatory capabilities (Forsman, 2000; Hegna et al, 2013; Lindstedt et al, 2009). As it has become possible to model the conspicuousness of different genotypes to different receivers (Endler & Basolo, 1998; Hart, 2001a; Henze et al, 2018), we may soon be able to estimate how their appearance shapes the fate of allelic combinations using long‐term data sets (Le Rouzic et al, 2015; Svensson & Abbott, 2005).…”