Researchers studying primates in Ethiopia discovered an unexpected and close sexual bond between a male donkey named Patroclo and a bull named Achille. Over four days of observation, scientists recorded 51 mountings and frequent affectionate behaviors, offering new insight into animal social relationships outside of reproduction.
Fieldwork rarely unfolds exactly as planned. When evolutionary biologist Elisabetta Palagi of the University of Pisa in Italy sent a student team to the Ethiopian highlands to observe geladas, the researchers found themselves distracted by an entirely different pair of animals sharing the plateau (Popular Science).
How André da Cruz First Spotted Achille and Patroclo in Ethiopia
The unusual interspecies relationship came to light entirely by accident. While taking a midday break from monitoring bleeding-heart monkeys, PhD student André B. da Cruz noticed a striking interaction unfolding across the grass (Scientific American). The scientific community is paying attention to the special relationship between a male cow and a male donkey discovered in a pasture in Ethiopia, Africa, as noted in research published in the international academic journal Current Biology.
We were having a little break for lunch, and in the distance I see something – it seemed a bit odd. I told colleagues: ‘I think I saw a bull mounting a donkey.’ And they didn’t believe me.
André B. da Cruz, PhD student at the University of Pisa and NOVA University of Lisbon
The animals belonged to different owners and only encountered each other when their respective herds grazed in the same shared pasture The Guardian. Intrigued by the sighting, Palagi’s team set up a formal observation protocol, tracking the pair across four days when they grazed together and four days when only one was present Scientific American.
Detailed Observations of 51 Mountings and Affiliative Behaviors
During their structured observations between March 6 and March 19 (Popular Science), the researchers documented Achille mounting Patroclo a total of 51 times Defector. Of those mountings, 34 resulted in penetration Defector. Unlike typical donkey behavior—where animals usually kick, flee, or pin their ears back in resistance to unwanted advances—Patroclo showed no avoidance The Chosun Ilbo.
The interactions extended well beyond mounting. The bull and donkey routinely licked, rubbed, and nuzzled one another before and after sexual acts The Guardian. When Achille briefly mounted another male donkey on a couple of occasions, that animal reacted with immediate aggression and flattened ears The Chosun Ilbo. By contrast, Patroclo actively maintained his bond with Achille, stepping in to distract the bull when Achille approached other cattle The Guardian. According to researchers, the bull may have been orgasming during these interactions, though complete verification remains impossible.
