Effect of ivermectin and dung beetle communities on dung removal rate in cattle pastures

Abstract

Despite the growing interest of cattle producers in maintaining and even favoring dung beetle communities in their pastures to remove dung, dung beetle species diversity has declined in tropical landscapes due to habitat loss and livestock management practices, in particular, the intensive use of the antiparasitic drug ivermectin (IVM). Among macrocyclic lactones, IVM has become the most widely used antiparasitic drug worldwide. Residues of IVM in the dung of treated animals have the potential to adversely affect non-target dung-breeding insects involved in pasture functioning, like dung beetles, whose primary function, dung removal, represents a key ecosystem service as it facilitates dung degradation and nutrient redistribution in soil. In this study, we compared removal rates of dung with and without IVM in 24 cattle pastures that either or not use this anthelmintic and analysed the relation of dung removal with dung beetle (Coleoptera: Scarabaeidae, Scarabaeinae) community attributes. We found higher dung removal rates in traps with IVM than in dung without it, although there were no differences in the amount of dung removed in pastures that use IVM or not. Dung beetle richness and number of individuals were the community attributes most strongly related to dung removal. Our results highlight the danger of the attractant effect of IVM on dung beetle communities in the study area, showing the importance of conducting field evaluations by monitoring the effects of macrocyclic lactones on this group of insects.