Multitrophic effects of colony-level variation in red imported fire ant foraging behavior

Intraspecific variation in behavior appears to be widespread among social insects, but the ecological impacts of such colony-level differences are poorly documented.  We provide the first empirical test of the multitrophic effects of colony-level behavioral variation of a widespread and invasive social insect pest.  Red imported fire ant colonies (Solenopsis invicta) differ consistently in their foraging activity and effort at different resources.  We quantified this variation and assayed the direct and indirect impacts of these colony-level differences on an insect herbivore and its host plant.  Colonies with higher foraging activity at carbohydrates predated caterpillars significantly faster and reduced herbivory damage of cotton plants by as much as seven fold.  Colony differences in foraging activity at proteins improved predictions of ant effects on caterpillar mortality only when differences in carbohydrate foraging were first accounted for.  Our study demonstrates that colony-level behavioral variation can have dramatic, cascading consequences for other organisms, and suggests that differences in carbohydrate-attraction may drive variation in the ecological impacts of fire ants.  Incorporating differences in nutritional ecology may improve our ability to predict variable effects of social insects on other organisms.