A Bull and a Donkey in Ethiopia Formed an Unexpected Bond, Researchers Report

Researchers working in the Ethiopian highlands have documented what they describe as the first sustained same-sex sexual relationship between a bull and a donkey. The observations, reported in the journal Current Biology, suggest the two animals shared a selective social bond that went beyond sex, according to ScienceAlert.

The team had gone to study gelada monkeys when they happened to notice the pair in a nearby grazing area.

What the researchers saw

Over a number of days, a bull named Achille was observed mounting a male donkey named Patroclo. Mounting was documented 51 times, and 34 of those events involved penetration, the researchers reported.

The behavior was not random. When Achille tried the same thing with another male donkey in the pasture, that donkey showed clear avoidance, including flattening its ears in a threatening expression. Patroclo, by contrast, never avoided or kicked away the bull and appeared to present his hindquarters to him.

More than sex

The two animals also exchanged friendly behaviors such as licking, rubbing and nuzzling more often with each other than with other animals, and those exchanges lasted longer. They spent most of the observed time close together.

University of Pisa ethologist Elisabetta Palagi, who led the work, told ScienceAlert that the sexual interactions were one part of a much broader, selective relationship. Both animals had access to other potential partners, including animals of their own species and of both sexes, she said, yet they repeatedly sought each other out.

The team also noted that contact before mounting, such as licking and nuzzling, is not unexpected between animals because it can help make mounting possible. What stood out was that Achille and Patroclo engaged in interactions after mounting much more often than any foreplay. In their paper, the authors say this suggests the behavior may signal relationship quality and help prolong the social interaction beyond the sexual act, rather than being explained by arousal alone.

On another occasion, when Achille mounted a different donkey, Patroclo moved in close, as if to prevent further contact between them. Achille ended up interacting with Patroclo instead, including licking his body.

Why it matters

Same-sex sexual behavior is widespread among animals, ScienceAlert noted, but sexual encounters between different species are much rarer. A pairing that appears to have lasted, and that involved a clear preference on both sides, adds to evidence that animal sexual behavior can be a more complex social phenomenon than many people assume.

Palagi said the most surprising part was how selective and consistent the association was, especially because the animals had different owners and spent their nights apart, meeting only during daily grazing. Her broader point was that unusual behavior can remain anecdotal simply because nobody has the chance to document it systematically.

The article cautions that no one can know exactly what the relationship meant to the animals, and that their interactions should not be read through a human lens. The researchers describe it as suggestive of a social bond that crossed a species boundary.

What happens next

It is uncertain whether the bond still exists. After the study, Achille and Patroclo were moved to different grazing areas. The researchers hope to return to see whether the animals resume their activities and to investigate whether similar relationships between species occur more often than scientists realize.

The findings are based on field observations of a single pair, so they cannot show how common such bonds are.

Around Prague, based on reporting by ScienceAlert, The Guardian