Attractiveness of dung from ivermectin-treated cattle to Danish and afrotropical scarabaeid dung beetles.

The effect of ivermectin treatment of cattle on the attractiveness of dung to scarabaeid dung beetles was assessed by pitfall trapping in Denmark, Tanzania and Zimbabwe. Traps were baited with dung collected at intervals after heifers were treated with ivermectin by subcutaneous injection (0.2 mg kg-1 body weight). In one Danish trial, beetles preferred control dung from untreated cattle, whereas no preference was found in two other experiments. In Tanzania, the overall tendency for beetles was also to prefer control dung. In Zimbabwe, two species (Euoniticellus intermedius and Liatongus militaris) were particularly attracted to dung from treated cattle, whereas three others did not discriminate between dung types. It is concluded that at least in some cases the attractiveness of cattle dung to scarabaeid beetles is affected by avermectin therapy. Beetle discrimination between dung types is probably attributable to some unknown side effect of the treatment rather than being a direct response to the drug itself.