Effects of novelty and gregariousness in survival of aposematic prey

Abstract

We examined the reactions of captive wild great tits to novel unpalatable prey with (1) a traditional aposematic signal (black and yellow) (2) a novel signal (light pink), and (3) a control signal (brown). Prey were offered either singly or in groups to see whether novel signals with fewer possibilities for synergistic benefits are more dependent on grouping than are the traditional signals. Indeed, responses of birds toward unpalatable prey depended significantly on spatial distribution of prey (grouping versus solitary) and the type of the signal. Birds avoided more the traditional black and yellow signals than novel pink signals in both experimental set ups, but both of these prey items survived better in aggregation than solitarily. The success of traditional signals may demonstrate the importance of synergistic selection across species in the evolution of warning coloration (i.e., Mullerian mimicry). Unpalatable prey individuals benefit strongly from using similar color patterns. Our results suggest that aggregation may be important for the evolution of novel signals in particular, even if a synergistic selection component is also present.