- Dung beetles provide recognised environmental services in cattle production systems, but can be negatively affected by the pharmaceutical residues found in excreta, particularly macrocyclic lactones (ML).
- The diversity and seasonal abundance of dung beetle communities were measured using baited pitfall traps and compared at four cattle ranches in Yucatan, Mexico, to assess the possible effects of ML residues. Cattle parasite control was performed at two of these ranches using ML.
- A total of 93 274 dung beetles from 17 species were collected. The dominant species at all four ranches were Onthophagus landolti and Canthon indigaceus chevrolati. Compared to ranches where ML was not used, total abundance was higher but richness, evenness and diversity were lower at ranches where ML was used. Five other species were identified as potential indicator species for determining whether there was an effect of ML use at the studied ranches.
- Seasonal patterns differed between beetle communities: those found at non-ML sites occurred in higher abundances in May and July, while those at ML sites had higher abundances in May and June. This was probably because herds on ML sites were treated with ML to control parasites in early July.
- The application of ML for controlling cattle parasites was shown to have a negative effect on the diversity and abundance of dung beetles. These results emphasise the need for timing ML use in order to mitigate the adverse impacts on these insects.