Bull and Male Donkey Form Unusual Bond
Researchers from the Università di Pisa observed 51 mountings between the two animals in just 13 days, despite having access to other potential partners
An unusual sexual bond between a bull and a male donkey has been observed by researchers from the Università di Pisa (UNIPI) in Tuscany, Italy. The bond, which was characterized by repeated mounting behavior and affiliative interactions, was formed between a bull named Achille and a male donkey named Patroclo.
The researchers, led by authors Elisabetta Palagi, André da Cruz, and Martina Francesconi, witnessed 51 mountings between the bull and donkey from March 6 to March 19, 2026. This behavior was not isolated, as the two animals consistently chose each other as partners despite having access to other potential partners, including individuals of both sexes and of their own species.
The bull, Achille, mounted another male donkey only twice, and that other male showed clear avoidance behaviors and threatening expressions. In contrast, Patroclo, the male donkey, often presented his hindquarters to Achille and nipped him during interactions. The researchers recorded all interactions they witnessed involving either Achille or Patroclo and found that the two animals repeatedly directed most of their social and sexual interactions toward each other.
The study, which was published in the journal Current Biology on November 2, 2026, provides insight into the complexity of animal relationships. The observations were made while the researchers were conducting another study in the field, and they were surprised to see the strong bond between the two animals.
## Why it matters The observation of this unusual bond highlights the diversity of animal relationships and challenges traditional views of animal behavior. The fact that the two animals chose each other as partners despite having access to other potential partners suggests that their bond was based on a strong social connection. This study contributes to our understanding of animal behavior and social interactions, and it has implications for our understanding of the complexity of animal relationships.
The study's findings also raise questions about the nature of animal attraction and the factors that influence animal behavior. The researchers' observation of the repeated mounting behavior and affiliative interactions between the bull and donkey suggests that their bond was characterized by a strong emotional connection. Further research is needed to fully understand the implications of this study and to explore the complexity of animal relationships.
