Impact of blood parasites on the behaviour of two congeneric wall lizards (genus Podarcis)

Abstract

Modern studies have shown how parasites add extra complexity to ecosystems through their potential effects on hosts. Blood parasites are common in lizards and various studies have suggested varying degrees of negative effects on these hosts. In this study, we investigate effects of infection by blood parasites on the boldness and aggressiveness of male lizards of two sympatric species living in North Portugal: Podarcis bocagei and Podarcis lusitanicus, known to host blood parasites of two protozoan orders: Adeleorina and Eimeriorina (Apicomplexa). We used a mirror to quantify behavioural interactions of the lizards with their specular images, which did not identify any influence of parasite infection on either species. Boldness was evaluated through exploratory tests, with an identified trend for parasitized P. lusitanicus towards higher exploratory activity and exposure time. This was independent of the intensity of infection. No such effect was found for P. bocagei. The behavioural changes for infected P. lusitanicus appear to be in the direction of increasing light exposure by spending more time directly under the light source, thus suggesting a link with thermoregulation, although further experiments to clarify this hypothesis are required. These results highlight the importance of understanding individual parasite-host relationships, as they show that the same parasites can have different effects across even closely related species.