Asian elephants with longer tusks have lower parasite loads

The Hamilton and Zuk hypothesis that the intensity of male ornamentation allows females to assess a male's ability to resist parasites has been much debated recently. Much of the empirical work to test this hypothesis has been with insect, fish, reptilian or avian hosts. In a southern Indian population, we show that the length of tusks of male Asian elephants (Elephas maximus), corrected for differences due to age, is significantly negatively correlated with intestinal parasite loads. The less aggregated distribution of parasites in this elephant population, as compared to other mammalian species, indicates that ivory poaching may have already selectively removed a significant proportion of parasite-resistant individuals. Ivory poaching which targets larger-tusked elephants may thus affect the health status of the population.