Kristoffer H Wild, Christopher M Gienger

Host-parasite relationships are important components of ecological systems that influence the evolution of both hosts and parasites. High levels of ectoparasitic infections can disrupt host homeostasis, causing adverse effects on health and performance. However, the effects of natural ectoparasitic levels on host physiology are less understood, with most research designs implementing experimental or hormonal manipulations of hosts. In this study, we examined the interplay between tick parasitism and host characteristics on body condition and locomotor performance in Eastern fence lizards in natural settings. We found a higher prevalence of tick infections in male lizards relative to females, with larger males being more likely to experience tick infection. Infected lizards appear to exhibit an energetic trade-off between increased immune function and reduced locomotor performance, which is consistent with the immunocompetence-handicap hypothesis. Higher prevalence of tick infections in adult male lizards may be explained by age as well as the immunosuppressive effects of testosterone. Tick infection did not appear to reduce overall body condition of lizard hosts. Our findings shed light on the interplay between ectoparasitic infection, host characteristics, and locomotor performance under natural conditions. Such insights are crucial for understanding host-parasite dynamics and determining the trade-offs for hosts within ecological contexts.