Prevalence and intensity of blood parasites in insular lizards

Parasites are important in understanding population dynamics and ecology of hosts. In several Mediterranean islands, little is known about lizards' blood parasites. We studied the relations between haemoparasites and an endemic lizard host, Podarcis lilfordi (Günther, 1874) on Aire Island (Menorca, Balearic Islands, Spain). The infection intensity was about 1% of the red blood cells and 95% of the individuals were infected. These values are higher than in continental populations of the genus Podarcis. The reduced genetic variability and/or the high density in islands are proposed to explain such differences. More adults than juveniles were infected, probably because they were more often exposed to parasites during their lifetime. In adult lizards, prevalence was higher in males, may be as a consequence of their higher activity levels and more frequent physical contacts during male-male interactions. We found that infected individuals were larger than uninfected ones. A higher prevalence in adults is responsible of these differences. The intensity of infection was similar between age and sex classes. Prevalence remains stable between seasons, while parasite load increases in summer, as the availability of resources and body condition decreases. We found a relation between prevalence, intensity and body condition, with a higher prevalence and parasite load in individuals with lower condition.