Researchers studying geladas in Ethiopia came across an unexpected subject: a bull and a donkey that repeatedly sought each other out in a shared pasture near Debre Libanos. The team, led by University of Pisa ethologist Elisabetta Palagi, had been working in the area for years to study how the monkeys resolve conflicts when they first witnessed the animals mating.
After the initial encounter, the researchers followed the pair, Achille the bull and Patroclo the donkey, recording approaches, physical contact, mating and fights. Over a period of less than two weeks, Achille mounted Patroclo 51 times, including 34 instances of penetration. Patroclo did not resist and often presented his hindquarters to the bull, according to the account of the observations.
The researchers also recorded affiliative contact after mating, including touching, nibbling and rubbing. They considered this behavior significant because it suggested the interaction continued socially beyond mating. The pair spent more time together than apart, despite cows and donkeys being nearby.
The observations led the team to distinguish the relationship from other proposed explanations for sexual behavior between different species, such as coercion or a lack of available females. The researchers instead found signs of reciprocal behavior and social attachment. Local herders reportedly recognized the scene, while the researchers had initially been surprised by it.
The account describes the case as the first of its kind to be documented in this detail. It also notes that a 2024 University of Toronto survey of 65 mammal specialists found that 77% had observed same-sex sexual behavior in the species they studied, while 18% had published observations of it.
Sources: Xataka.