METAANALYSIS OF PARASITE-INDUCED BEHAVIORAL-CHANGES

A meta-analysis was performed on published results of studies measuring the effects of helminth parasites on host behaviour. For each of the 114 comparisons between infected and uninfected hosts that could be included, an estimate of the magnitude of the effect of parasites was calculated and standardized for the variability in the original data. Using these estimates, the meta-analysis then determined the overall magnitude and significance of the effect of parasites on host behaviour, and tested for consistency among the outcomes of different comparisons. Significant differences were found between helminth taxa, with nematodes having a greater effect on both host activity and microhabitat choice than other helminth parasites. The magnitude of the effect of parasites on host activity was similar whether the host was an invertebrate or a vertebrate, but the influence of parasites on host microhabitat choice was greater in vertebrates. Contrary to what had been expected, parasites that do not appear to benefit from changes in host behaviour had the greatest impact on host behaviour, although taxonomic biases may have affected this comparison. The meta-analysis has uncovered trends and raised several questions that should be addressed in future studies. © 1993 The Association for the Study of Animal Behaviour.