Mate detection and seasonal variation in stick insect mating behaviour (Phamatodea: Clitarchus hookeri)

Abstract

For animals that exhibit a scramble competition mating system, sexual selection pressures on mate searching ability are expected to be strong. Scramble competition mating systems evolve when populations provide females with equal accessibility to all male competitors, yet sex ratio and population density influences mating systems and varies seasonally. The stick insect species,Clitarchus hookeri, is frequently found in copula, yet very little is known about it’s mating behaviour. We preformed behavioural tests and assayed antennal sensory morphology to determine whether males used chemosensory cues to detect females. Through natural field observations we found populations to be significantly male-biased earlier in the season, while later, populations began to display equal sex ratios. With increasing female availability mating pair proportions steadily increased, while copulation duration declined. These results supportC. hookerias a scramble competitor, and demonstrate males may alter their behaviour in response to the seasonal variation in female density.