Did aggregation favour the initial evolution of warning coloration? A novel world revisited

From experiments using novel prey signals to avoid innate reactions to trad itional signals, Alatalo & Mappes (1996, Nature, 382, 708-710) concluded th at gregariousness would have selected for warning coloration as it originat ed for the first time, whereas a solitary prey distribution would not. We h ave investigated this suggestion in experiments using the same novel prey a nd background symbols and wild-caught great tit, Parus major, predators. We compared the attack rate on cryptic unpalatable and aposematic unpalatable prey in either a solitary or an aggregated treatment. In the aggregated tr eatment we: found no difference in attack rate on cryptic and aposematic-pr ey. In the solitary treatment the attack rate on aposematic prey was signif icantly lower after one attack and at the end of the experiment. Thus, we c onclude that, in so far as these experiments mimic an original predator-pre y relationship, they do not give support to the idea that aggregation would have favoured the evolution of warning coloration in unpalatable prey. (C) 2000 The Association for the Study of Animal Behaviour.