Meeting Abstract
Although many pathogens cause host mortality by directly damaging host tissues, others increase mortality through indirect mechanisms. Among the best studied of these is an increased risk of predation during infection, particularly for systems in which pathogens are transmitted trophically from prey to predators. However, in systems without trophic transmission, we know considerably less about the impacts of infection on anti-predator defenses and the mechanisms involved. Here we tested how Mycoplasma gallisepticum, an emerging pathogen of wild birds that is not transmitted across trophic levels, impacts anti-predator behaviors in its primary free-living host species, the house finch (Haemorhous mexicanus). Using wild-caught finches in a controlled laboratory environment, we found that infected birds spent more time near a stuff predator (Cooper’s hawk) while feeding than did uninfected birds. Additionally, during a simulated predation attempt (hand capture by researchers) infected birds were captured significantly more rapidly. Because this pathogen induces both severe swelling around the eyes and pronounced sickness behaviors (e.g., lethargy) in house finches, obscured vision and diminished locomotion could each play a role in reducing anti-predator behaviors. However, when we excluded birds with visible eye swelling from our analyses, infected birds still exhibited reduced anti-predation behaviors, suggesting a primary role for lethargy or other sickness behaviors in these differences. More broadly, our results suggest that the costs of sickness behaviors include reduced anti-predator behaviors, even in non-trophically transmitted infections.
