Achille and Patroclo: the bull and donkey who sought each other out in Ethiopia

On a plateau in Ethiopia, a bull and a donkey sought each other out for more than just sharing the landscape: they approached, rubbed against each other and engaged in sexual interactions. Achille and Patroclo, from different species, are at the centre of a case that invites us to look more closely at animals’ social lives. Without binoculars, mind you, it might be hard to tell which one has come to say hello and which to start courting.

Martina Francesconi, André B. da Cruz and other researchers from the University of Pisa came across the pair by chance while studying geladas. The study was published in the journal *Current Biology* on 2 November 2026. Their names evoke the heroes of the *Iliad*, known for the close bond between them: a rather epic literary choice for two four-legged neighbours.

Between 6 and 19 March 2026, the researchers carried out systematic observations. Both animals were present on four days, while on another four only one of them was there. According to the herders, Achille and Patroclo belonged to different owners and spent their nights apart. Their encounters were therefore not a case of living together permanently under the same roof, but of a relationship developing on shared ground.

During the observations, researchers recorded 51 mounts by Achille on Patroclo. But the case is interesting for more than that figure, which seems enough to fill a dating diary. There was also licking, rubbing and muzzle-to-body contact. Patroclo took part in the interactions: he presented his hindquarters to the bull and gave him small bites, according to the study’s description as reported by *La Vanguardia*.

The donkey’s behaviour also drew attention because he did not show the avoidance or defensive responses seen in other donkeys during this type of interaction. The researchers describe the bond as selective: the two animals sought each other out and combined mounting with social contact. In other words, they were not two strangers bumping into each other by chance in a corner of the meadow.

What is more, both had access to animals of their own species and of both sexes. According to the University of Pisa researchers, a lack of alternatives is not enough to explain why they chose to maintain this relationship between different species. The case offers a way to explore how sexual behaviour can form part of social life and need not be limited to reproduction. The researchers suggest that these interactions might strengthen the bond, reduce tension or serve another purpose, but these are possibilities, not proven conclusions.

Achille and Patroclo offer a small but intriguing glimpse into the variety of relationships animals can form. A pair observed over a few days does not establish a rule for bulls and donkeys; it does remind us that companionship and affinity do not always fit into our boxes, as neatly arranged as a freshly swept stable.

Curious fact: the team came across Achille and Patroclo while researching geladas, primates from Ethiopia.

By Darwi-IA Silvestre, La Gaceta de Guardamar’s virtual nature reporter, an artificial intelligence: produced using publicly available sources. Sources consulted: unipi.it, cdn., .