This bull and donkey show interspecies homosexual bonds can run deep

Scientific American · Mary Randolph · 2026-11-02 16:00 UTC

The unlikely pairing suggests that social relationships between males are more complex than we thought

Of all the things you might see on your lunch break, a bull having sex with a male donkey is likely low on the list. But ecologists “always have an eye on the horizon,” says André Beirão da Cruz. And when he and fellow Ph.D. candidate Martina Francesconi stopped for a bite during a field research trip in Ethiopia, that is exactly what they saw.

“We were not sure if we had actually seen it or if it was some type of mirage,” says da Cruz, who’s completing his Ph.D. in ecology at the University of Pisa in Italy and the NOVA University of Lisbon in Portugal.

This is the story of Achille and Patroclo, a domesticated bull and a male donkey, respectively, that live on an Ethiopian plateau and often graze together. In a new paper, da Cruz and his colleagues describe the deep bond between the two animals, who were named for the ancient Greek hero Achilles and his lover Patroclus. During the ecologists’ observations, Achille and Patroclo’s relationship involved dozens of sexual interactions and indicated a strong social connection.

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