Absence of measurable malaria-induced mortality in western fence lizards (Sceloporus occidentalis) in nature: a 4-year study of annual and over-winter mortality.

Theoretical models of parasite virulence often quantify virulence by mortality. However, there is a lack of empirical studies of parasite-induced host mortality because it is often difficult to quantify in natural populations. I have estimated annual and over-winter mortality in a population of fence lizards (Sceloporus occidentalis) infected with a malaria parasite, Plasmodium mexicanum, in northern California. The duration of time a lizard was observed (an estimate of life-span) throughout the 4-year observation period, or following winter, was not related to either infection status or maximum parasitemia. In contrast to previous laboratory studies of this parasite-host system, I found no evidence of parasite-induced host mortality in nature.