Overview
- The study, published in the journal Primates, compiled 427 documented cases of positive interspecies social behaviour drawn from 303 scientific reports, 58 media accounts and 66 primatologist survey responses.
- Researchers found play (139 cases) and grooming (136 cases) were the most common behaviours, with juveniles more likely to play, adult females more likely to groom, and adult males least likely to engage.
- The dataset spans 88 primate species and 127 partner species, and includes examples such as macaques grooming dogs in Thailand, langurs touching squirrels in Sri Lanka, snub-nosed monkeys playing with pigs in China, and capuchins adopting a marmoset in Brazil.
- Not all encounters were safe: the authors recorded 13 partner deaths and noted curiosity or caregiving sometimes led to harm, underscoring risks for animals in the wild and in mixed-species facilities.
- The team argues these heterospecific relationships may be evolutionary building blocks for human-animal companionship and recommends systematic recording during long-term field studies to guide zoo, sanctuary and conservation management.