Evolution of conspicuous warning signals

Aposematic species use conspicuous signals to advertise their unprofitability as prey to potential predators. Conspicuousness is advantageous since, predators learn to associate unprofitability to conspicuousness and to avoid these species more effectively than cryptic unpalatable prey. However, conspicuous individuals are more prone to detection and therefore the evolution of aposematism seems paradoxical. If the conspicuousness increases the likelihood of predator detecting the prey, and presumably predation, how can it be advantageous for the prey individuals initially. In the first experiment I tested, whether three classes of great tits (Pants major) naïve, yearling and adults possess preferences originating from either their genetic or cultural history. Not only experienced predators (yearling and adults), but also naïve birds preferred brown prey over yellow and black prey. Since even naïve birds possess some avoidance towards typical warning colours, it leads to restrictions for studying initial evolution of aposematism experimentally. To diminish the effects of the evolutionary history of predators I have used a "novel world" method, where instead of colours the world consists of symbols. Thus, I'm able to study relative selection pressures from predation on evolving conspicuous prey. These results indicate that the predator psychology, namely as reactions against novel prey and as avoidance learning can create different selection pressures on conspicuous aposematic prey. When highly conspicuous novel prey is introduced to experienced predators the visibility costs are counterbalanced by predator neophobia. Since birds learnt to avoid only very conspicuous prey, the gradual evolution as a change in conspicuousness does not seem to be a plausible explanation for the evolution of warning colours. However, since gregariousness aided the survival of even non-conspicuous unpalatable prey by immediate effect, grouping might have facilitated even gradual evolution. When gregarious prey was conspicuous, the grouping aided also avoidance learning. However predation was anti-apostatic, and low frequencies suffered greatly from increased predation. Birds learned to avoid aposematic prey in all frequencies but learning was not dependent on the number of unpalatable prey birds ate. In all frequencies aggregated prey suffered less from predation. These results indicate that the evolution of conspicuousness might be facilitated by several mechanisms, which are not mutually exclusive.