Meeting Abstract
Migratory animals undergo extreme physiological changes to prepare for and sustain migratory movements such as flight. One of these changes is investment in immune defenses. Importantly, the intense energetic demands of migration can divert resources away from immunity, increasing susceptibility to parasites and pathogens. However, some migrants also atrophy reproductive organs, and these non-reproductive migratory animals could experience lower energetic costs during migration. In this study, we quantified the costs of flight for immunity in monarch butterflies and examined whether these costs further depend on reproductive investment by controlling whether or not monarchs were in a pre-migratory state of reproductive diapause prior to flight. Direct physiological linkages between flight and immunosuppression are poorly described in wild animal populations. We used a tethered flight mill apparatus to mimic the demands of powered flight and address several inter-related questions. First, we measured whether immunity differed in monarchs that were flown versus those that remained inactive. Second, we examined relationships between continuous measures flight performance and immunity. Last, we determined if reproductive investment compounds the cost of strenuous activity for immune defense, by comparing immune-flight relationships in reproductive and non-reproductive monarchs. Our work shows how multiple behavioral drivers affect immune defense, with the potential to identify the mechanisms and circumstances under which migratory species are most vulnerable to disease.
