Effects of Natural and Sexual Selection on the Evolution of Guenon Loud Calls

Abstract

In the Taï Forest, most guenon loud calls show many properties of classic alarm calls: they advertise perception to predators and warn recipients about the presence of specific predators, suggesting that they have evolved through natural selection. However, several lines of evidence, such as sexual dimorphism in call structure, consistent call usage in non-predatory situations, and ontogenetic evidence suggest that loud calls have been under pressure from sexual selection. Sexual selection seems to have caused the evolutionary transition from regular alarm calls to the structurally distinct loud calls, by selectively affecting the calls’ transmission features and by favoring call usage to indicate male quality. In the polygynous mating system of the forest guenons, male competition over females is especially high and this mating system is notorious for leading to the evolution of conspicuous male traits through sexual selection. Male guenon loud calls are another example to be added to the list (Anderson, 1994).