Does Neem trigger the same response as Ivermectin? Dung beetle behaviour and physiology

Potential negative effects of the synthetic veterinary pharmaceutical, Ivermectin, on non-target fauna have generated a search for less-toxic alternatives. Thus, Neem plant extract ( Azadirachta indica A. Juss) has been used as a natural alternative to replace Ivermectin worldwide. However, little is known about the effects of this natural veterinary pharmaceutical’s residues on the behaviour and physiology of adult dung beetles (Coleoptera: Scarabaeinae), which use livestock dung as a feeding and nesting resource. To understand such effects, we performed a non-choice experiment using Dichotomius nisus Oliver, 1798. We evaluated effects of Neem and Ivermectin residues on the ecological functions of dung burial and soil bioturbation performed by dung beetles. Additionally, we performed Soxhlet extraction of dung beetle body fat content to evaluate physiological stress in response to ingestion of Ivermectin or Neem. Our results showed that D. nisus do not alter their behaviour in the presence of Neem and Ivermectin residues in dung when contrasted with the control after 48 hours. However, individuals feeding on dung with Ivermectin residues for a period of twenty days had 5% more body fat content than those from control and Neem treatments. Our findings provide the first evidence that Neem can be a less toxic alternative to non-target fauna than Ivermectin.