🌅 A Surprisingly Sexual Interspecies Relationship

SOURCE

da Cruz et al. (2026)

WHAT TO KNOW

• Researchers from the University of Pisa in Italy observed a bull named Achille mount a male donkey named Patroclo 51 times over four days as the pair grazed together on the Ethiopian plateau, including 34 mountings that involved penetration. The researchers found Patroclo often initiated encounters by presenting his hindquarters to Achille and nipping at him, and the pair often displayed affectionate behaviors like licking and rubbing after their rendezvous. Observations also showed the animals repeatedly chose to spend time together and specifically selected each other for the sexual encounters, despite the availability of other members of their species.

WHY IT MATTERS

• Same-sex sexual behavior is widespread among animals and well-studied by researchers, however, interspecies sex is far more rare (hybrids are the result of two species successfully reproducing). Most known instances of interspecies sex, like Japanese macaques mounting sika deer, also lack mutual sexual interest, unlike the apparently reciprocal relationship between Achille and Patroclo. The authors of the present study further found that the sexual encounters between Achille and Patroclo formed part of a highly selective and consistent relationship, raising broader questions about sexual behavior as a social trait beyond reproduction.

CONNECT THE DOTS

• Same-sex behavior has been reported among more than 1,500 animal species, including penguins, bonobos, and dolphins. A 2023 study documented same-sex behavior in 261 mammalian species, finding it was particularly associated with social species, suggesting it could play a role in maintaining relationships and managing conflict. Research on nonhuman primates suggests same-sex behavior may reinforce social bonds and help animals survive longer, particularly in harsh environments or within strict social structures, indicating it might provide some evolutionary advantage.