Dispersal of dung containing ivermectin in the field by Onthophagus taurus (Coleoptera: Scarabaeidae)

Fifty-five species of exotic dung beetles have been introduced into Australia and in many areas, several species are now established and often abundant. Controversy exists in the dung beetle literature concerning the use of ivermectin as an anthelmintic treatment for livestock and its subsequent lethal and sub-lethal effects on adult dung beetles. A study was conducted in the field exposing replicate dung pats containing residues of ivermectin excreted 0–15 days post-injection. At the time of the study, the introduced species of dung beetle Onthophagus taurus (Schreber) was present in high numbers (>1000 beetles per pat). After 24 h exposure, dung pats collected from cattle treated 7 and 10 days earlier with ivermectin were dispersed significantly less than untreated dung. A similar pattern was evident in the numbers of dung beetles present in each pat. This study is discussed in the context of anthelmintic usage in cattle and their potential ecotoxic effects against dung beetles.