Effects of Nymphal Ticks and Their Interaction with Malaria on the Physiology of Male Fence Lizards

Abstract

Ectoparasites infest many lizard species, but the physiological consequences of infestation in free-living lizards have not been studied. We examined male western fence lizards, Sceloporus occidentalis, infested with ticks, Ixodes pacificus, in northern California. Many lizards in this population were also infected with malaria, Plasmodium mexicanum. We found that the effects of nymphal ticks on blood composition and body condition (relative body weight) depended on the age of the lizard host and whether the lizard was also infected with malaria. Adult male lizards, but not juveniles, infested with ticks had lower hematocrits than uninfested lizards. Although the reduction in hematocrit that accompanies the mean level of tick infestation probably does not substantially affect the lizards, heavy infestations (>5 ticks per lizard) may significantly limit the aerobic capacity and behavior of the lizard host. Lizards parasitized with both ticks and malaria had significantly lower body condition than lizards with one or neither parasite.