Scientists baffled by ‘special relationship’ between donkey and bull
The case study focuses on Achille the bull and Patroclo the donkey, who live on an Ethiopian plateau and often graze in the same area. (André B da Cruz, UNIPI)
A new Current Biology paper describes a domesticated bull in Ethiopia mounting a male donkey 51 times over four days, with researchers saying the behaviour appeared to reflect a “special relationship” rather than a one-off encounter.
The case study focuses on Achille the bull and Patroclo the donkey, who live on an Ethiopian plateau and often graze in the same area.
Ecologists André Beirão da Cruz and Martina Francesconi first spotted the behaviour during fieldwork in Ethiopia, as described in Scientific American. Da Cruz recalled: “We were not sure if we had actually seen it or if it was some type of mirage,” after seeing what appeared to be a bull having sex with a male donkey.
Researchers then observed the pair for four days together and four days apart. During the four days they were together, Achille mounted Patroclo 51 times. The team also recorded licking and rubbing around the encounters, including after sexual interactions.
What did researchers observe between Achille and Patroclo?
The researchers described the behaviour as reciprocal rather than one-sided. Francesconi said Patroclo was receptive when Achille mounted him, but aggressive when other bulls were nearby.
The team observed Patroclo often presenting his hindquarters to Achille and nibbling him. The researchers’ view was that the licking and rubbing, including after sex, appeared to prolong social contact beyond the act itself.
Dr Elisabetta Palagi, an ecologist at the University of Pisa and a co-author of the study, said the behaviour was “really, really unusual,” adding: “And it is the first time it is reported in literature.”
What does it mean for how people talk about ‘natural’ sexuality?
Vincent Savolainen, an ecologist at Imperial College London who was not involved in the work, said the authors “show quite nicely that these two are not just a random dyad.” He also cautioned that because Achille and Patroclo are domesticated animals, it may be difficult to draw wider conclusions about wild populations.
Same-sex behaviour in animals is often pulled into culture-war arguments about whether homosexuality is “natural”, even though animal behaviour does not map neatly onto human identity. Author Josh Luke Davis said he would be “concerned about how it could be misconstrued or twisted by those who already deem homosexuality ‘unnatural’.”
Animal same-sex behaviour has been documented across many species. In 2023, a Nature Ecology & Evolution study of rhesus macaques found “most males were behaviourally bisexual” in a wild colony observed over three years, as reported in PinkNews.
