When virginity matters: age and mating status affect female responsiveness in crickets

Abstract

Behavioural assays in which animals recognize, localize or discriminate among signals are broadly useful for answering an array of biological questions, but results can be sensitive to the characteristics of individuals, including age and mating status. Researchers may prefer to use young, unmated individuals in experiments both to control for the effects of mating and because younger and unmated individuals may respond more often or more quickly. In natural contexts, virgin females are likely to behave differently than mated females, especially in animals that store sperm for future use, because the costs and benefits of mating are different for these two groups. In species in which multiple mating is common, individuals are much more likely to have mated at least once at the time of any given mating event than they are to be virgins, suggesting the use of virgin subjects in experiments is not reflective of most natural mating decisions. We conducted a literature review to sample the methods employed in empirical studies that use crickets in phonotaxis assays. Many studies draw conclusions based only on virgins, and methods vary widely with respect to the age of individual subjects. We then conducted an empirical study of the effect of mating status and age on female phonotaxis behaviour in Teleogryllus oceanicus, the Pacific field cricket. Our results show that both age and mating status affect some commonly used measures of female responsiveness in phonotaxis assays: older females begin moving more quickly in phonotaxis tests, while virgins have shorter response latencies. These findings are consistent with the idea that the cost of remaining unmated increases with age, and that virgin females benefit from an initial mating more than mated females benefit from additional matings.