Resolution of multi-receiver trade-offs in wall lizard colouration
Animal colouration evolves under multiple, often conflicting, selective pressures. Conspicuous, non-aposematic colour-patterns that enhance conspecific communication may simultaneously increase detectability by predators. Such trade-offs can be resolved by optimising colour-patterns to match the perceptual abilities of different receivers. We tested whether dorsal colour-patterns of the Lusitanian wall lizard (Podarcis lusitanicus) are optimised for ecologically relevant receivers across relevant viewing distances, while accounting for the visual acuity of conspecifics and predators. Conspecifics and snakes detected chromatic information at shorter distances, whereas achromatic and luminance information were detected at longer distances. Birds showed a uniform decline in detectability across the colour-pattern components with increasing viewing distance. Larger males retained high chromatic detectability across all receivers despite the general distance-related decline, whereas females and smaller individuals exhibited less salient colour patterns, consistent with predator avoidance strategy. Our results show that lizards resolve the trade-off between conspecific communication and predator detection through distance-dependent colour-pattern perceptibility across receivers. This resolution breaks down in large males, for whom the benefits of salient chromatic patterns for intraspecific communication may outweigh increased detectability to predators.