City life has fitness costs: Reduced body condition and increased parasite load in urban common wall lizards, Podarcis muralis

Abstract

Animals living in urban areas experience additional stress compared to those inhabiting more natural habitats. This could influence their physical state and ability to cope with parasites. Here, effects of environmental disturbances on body condition and prevalence and load of blood parasites in the common wall lizard (Podarcis muralis) were investigated by comparing these indices between five urban and five rural populations. The physical condition index was lower in urban areas, and females were the most affected sex. This suggests significant fitness costs, as survival and reproductive output are often tightly linked to body condition. Prevalence of blood parasites was more variable in urban (2.5–100%) compared to rural (50.0–75.6%) populations, with no statistically significant differences between the two habitats. Prevalence of blood parasites increased with body size. Parasite load was significantly higher in urban lizards, suggesting strong effects of urbanisation on host–parasite interaction. An increased concentration of blood parasites should affect fitness since various aspects of physiology are compromised in parasitised animals. Larger animals were more frequently and more severely infected, most likely due to their being longer and more frequently exposed to parasites. No differences between sexes in both prevalence and intensity were found, suggesting equal susceptibility or exposure to parasites.