A bull and a male donkey form a social and sexual bond

The two domesticated animals have different owners but often graze in the same field. Researchers observed them for four days together and four days apart. Patroclo was receptive when Achille mounted him but aggressive when other bulls were nearby; the pair also licked or rubbed each other after sexual interactions. An ecologist not involved in the research cautioned that this case may not reflect behavior in the wild.