Parasitism by bat flies (Diptera: Streblidae) on neotropical bats: effects of host body size, distribution, and abundance.

We examined the correlations between prevalence (proportion of infested individuals), mean intensity (number of parasites per infested individual), and the number of bat fly species parasitizing bats in Venezuela with host body mass, distribution, and abundance. Of 133 bat species sampled, 53 species in six families were captured frequently enough to allow estimation of their parasite loads. Over all species and six families, prevalence and mean intensity were uncorrelated with these variables, but the number of fly species was correlated with host body mass. Correlations of parasitism with body mass were strengthened among the 44 species of Phyllostomidae. Earlier studies showed that bat roosting habits influence their parasitism by bat flies with more permanent, enclosed roosts being with heavier parasitism. Multiple regressions of all measures of parasitism showed that roosting habits and host body mass, respectively, were the first variables to enter stepwise regressions, together accounting for 20-43% of the variation in measures of parasitism. Lack of correlation between proxies of distribution and abundance with parasitism is taken to indicate that proximate factors such as host-as-habitat, social groupings, and roost microhabitat take precedence over species-wide attributes like commonness and ubiquity.