An experimental test of condition-dependent mating behavior and habitat choice by water striders in the wild

Individual condition is expected to be an important determinant of many behaviors, including mating dynamics and habitat choice. In this study we experimentally investigated the linkages between individual condition, habitat use, and mating dynamics in the wild. We manipulated recent feeding history of the water strider, Aquarius remigis, and then quantified the habitat use and mating activity of males and females. Females could choose from three habitats (refuge, near shore, and open). On the water surface (open and near-shore habitats), in contrast to refuge, females can forage, but they are exposed to predation and sexual harassment by males. We tested three main hypotheses. First, we predicted that single females that were fed, relative to those that were not, would reduce their exposure to predators and male harassment by increasing their use of refuge. Similarly, we predicted that fed females that were mating would spend more time in refuge than those that were not fed. Our results support these two predictions. Fed single and mating females significantly increased their use of refuge. Third, we predicted that mating activity (proportion of time spent mating) of fed females would be reduced relative to starved females, because of reduced exposure to males while in refuge, and perhaps because of decreased receptivity to male mating attempts while on the water surface. Mating activity of fed females was about one third that of starved females. The decrease in mating activity could not be accounted for by any change in female receptivity, but could be accounted for by change in habitat use. The decrease in mating activity may have resulted from decreases in both mating frequency and mating duration. Our estimates of minimum mating frequency indicate a large and significant decrease, but we were unable to assess mating duration. We found no significant effect of our manipulation on habitat use or mating activity of males.