Effects of novelty and gregariousness in survival of aposematic prey

We examined the reactions of captive wild great tits to novelunpalatable prey with (1) a traditional aposematic signal (blackand yellow) (2) a novel signal (light pink), and (3) a controlsignal (brown). Prey were offered either singly or in groupsto see whether novel signals with fewer possibilities for synergisticbenefits are more dependent on grouping than are the traditionalsignals. Indeed, responses of birds toward unpalatable preydepended significantly on spatial distribution of prey (groupingversus solitary) and the type of the signal. Birds avoided morethe traditional black and yellow signals than novel pink signalsin both experimental set ups, but both of these prey items survivedbetter in aggregation than solitarily. The success of traditionalsignals may demonstrate the importance of synergistic selectionacross species in the evolution of warning coloration (i.e.,Müllerian mimicry). Unpalatable prey individuals benefitstrongly from using similar color patterns. Our results suggestthat aggregation may be important for the evolution of novelsignals in particular, even if a synergistic selection componentis also present