Monkeys grooming domestic dogs, gently petting squirrels and playing with pigs are among the 427 cases reviewed by researchers in a study published in Primates.
Play and grooming were the most common ways monkeys interacted with other species. Young animals were more likely to play, while adult females were more likely to engage in grooming. Adult males showed less interest in socializing with other species.
“The behavior cannot be equated with keeping pets, but may constitute some evolutionary building blocks for how companionship between humans and animals has developed,” says Cyril C Greuter at the University of Oxford in a comment.
