Fitness consequences of foraging success in water striders (Gerris remigis; Heteroptera: Gerridae)

Foraging theory's central premise assumes that behavioral actions that affect the acquisition of food also ultimately affect fitness. However, very few investigations in behavioral ecology actually demonstrate ultimate fitness consequences of any particular behavior. Many studies focus on short-term estimates of fitness in animals with considerable life spans. I investigated whether differences in foraging performance, as related to patch choice and behavioral dominance, show consistent patterns over extended periods of an animal's life such that they translate into differences in reproductive success. In one experiment, I focused on the ability of single female water strider (Gerris remigis) to discriminate between foraging patches of differing prey abundances in laboratory streams simulating natural conditions. In another experiment, I focused on competitive interactions within groups of three female water striders foraging in laboratory streams where resource availability varied with position in a patch. The first experiment showed that, overall, the individuals detected and preferred to forage in the richer patch, which directly increased their foraging success and their lifetime fecundity. However, there was marked variability among individuals in their ability to respond to the differences in food availability, ranging from no tracking to fast tracking when the patch qualities were switched. In the second experiment, both the foraging position of individuals in the stream and their dominance rank were reasonably consistent over their entire reproductive life. Foraging position and dominance rank were significant predictors of lifetime fecundity, the former being the better predictor due to an imperfect correlation between the two variables. In both experiments, the increase in fecundity was achieved by higher oviposition rates rather than by extending the oviposition period or by inducing first reproduction at an earlier age. [Behav Ecol 1991; 2: 46-55]