Adverse effects of ivermectin on the dung beetles,Caccobius jessoensisHarold, and rare species,Copris ochusMotschulsky andCopris acutidensMotschulsky (Coleoptera: Scarabaeidae), in Japan
AbstractEffects of the antiparasitic drug, ivermectin, on the dung beetles,Caccobius jessoensisHarold, 1867 and the rare species,Copris ochusMotschulsky, 1860 andCopris acutidensMotschulsky, 1860 were studied in laboratory and field experiments in Hokkaido, Japan. Ivermectin was detected in dung from 1 to 21 or 28 days following treatment, with a peak on the first day after treatment in two pour-on administrations (500 μg kg−1), although there were considerable differences between the two peaks. InC. jessoensis, brood balls constructed by the female were not reduced in the dung of treated cattle except for seven days after treatment in experiment 2. Also, there was no significant difference in the mean weight of brood balls between dung from treated and control cattle. However, the emergence rates were significantly reduced in dung 1–3 days after treatment. In the field study, brood balls constructed byC. jessoensiswere more abundant in dung from treated cattle in experiment 1, but adult emergence was significantly reduced at one and seven days after treatments. Adult mortality ofC. ochusMotschulsky at 90 days after the beginning of rearing was 11.1% in dung from control cattle with 22 brood balls constructed, whereas it was 84% in dung from treated cattle with no brood balls and/or ovipositioning. Also, inC. acutidensMotschulsky, adult mortality at 90 days after the beginning of rearing was 3.6% in dung from control cattle with 13 brood balls constructed, whereas it was 94.1% in dung from treated cattle with no brood balls or ovipositioning. The environmental risk in the use of ivermectin during breeding period of dung beetles in pasture is discussed.