Nectar, parasitism and flight in butterflies

When animals have unlimited access to food, they can often tolerate parasite infection and maintain high levels of growth and reproduction – but under food shortages, infected animals suffer more severe harm from parasites. This study examines the interactive consequences of food resources and parasitism for flight in a migratory insect, the monarch butterfly.  Migratory animals face extreme energetic demands during long migratory journeys, and some studies show that infected animals are less likely to survive long-distance migrations, in part owing to lower energy reserves of infected animals.  Monarchs are famous for undergoing a long-distance two-way bird like migration from breeding grounds as far north as Canada to wintering sites in southern Mexico.  Monarchs fuel their migration by accumulating lipid reserves from nectar resources during the fall. Monarchs are infected by a debilitating protozoan that replicates internally in caterpillars and pupae, and forms dormant spores on the outside of adults’ bodies. These parasites can lower monarch survival and reproduction, and past work showed that infected monarchs migrate less well than healthy butterflies. The proposed project test the flight performance of experimentally infected and healthy monarchs, fed different nectar diets. This study will examine the hypothesis that the flight performance of infected monarchs will suffer more under caloric restriction than the flight performance of healthy butterflies.

Mentors: Ashlew Ballew, Paola Barriga, Sonia Altizer
Type of project: Empirical, lab-based