Are whole-organism performance and thermal preference linked to endo- and ectoparasites in a short-lived lizard?

Wild animals are often concurrently infected by multiple parasites, which are assumed to negatively affect their host by exploiting the host's resources. The cumulative effect of parasite infections is often not studied. Despite this assumption, many hosts do not suffer significant costs from parasitism in the wild. Hosts can adapt to parasitic infections by mounting physiological and behavioural defences. A commonly used behavioural defence by ectotherms is to frequently visit warm environments to increase body temperature (i.e., behavioural fever) and thereby mount an immune response to parasites. Using the Australian common garden skink (Lampropholis guichenoti), we investigated the cumulative effect of endo- and ectoparasites on host performance. First, we investigated whether endo- and ectoparasites were associated with whole-organism performance in the lizards. Second, we explored whether host individuals responded to their parasite infection through thermoregulatory behaviour. We found no significant relationship between parasitism and body condition. However, the infection with ectoparasitic mites was significantly related to reduced sprint speed, while the nematode infection had no significant relationship with any of our three performance measures (sprint speed, endurance and foraging efficiency). We showed no evidence of behavioural fever and infected lizards did not differ in their body temperature from uninfected lizards. Our findings suggest that short-lived lizards may simply endure parasitic infections. The study provides an important example of how multiple infections with endo- and ectoparasites affect their host. It adds to the growing evidence for a negligible effect of parasites on host whole-organism performance.