Sex differences in the foraging behavior of a generalist hawkmoth

Abstract

Within-species variation in pollinator behavior is widely observed, but its causes have been minimally investigated. Pollinator sex is associated with large differences in behavior that may lead to predictable differences in flower foraging, but this expectation has not been explicitly tested. We investigate sex-associated differences in nectar-foraging behavior of the hawkmoth Hyles lineata, using pollen on the proboscis as a proxy for flower visitation. We tested two predictions emerging from the literature: 1) the sexes differ in the flower species they visit, 2) females are more specialized in flower choice. We also examined potential drivers underlying these predictions by performing field and laboratory experiments to test whether males 3) switch among flower species more frequently, or 4) fly farther and therefore encounter more species than females. Consistent with prediction 1), pollen load composition differed between the sexes, indicative of visitation differences. Contrary to prediction 2), females consistently carried more species-rich pollen loads than males. 3) Both sexes switched between flower species at similar rates, suggesting that differences in floral fidelity are unlikely to explain why females are less specialized than males. 4) Males flew longer distances than females; coupled with larger between-site differences in pollen composition for females, this result suggests that sex differences in mobility influence foraging, and that females may forage more frequently and in smaller areas than males. Together, our results demonstrate that sex-associated foraging differences can be large and consistent over time, and highlight the importance of sex as a driver of variation in pollinator behavior.