Primate Inter-Species Care May Reveal Early Roots of Human Pet Keeping

Researchers observed two young eastern chimpanzees, Ishe and Dembe, in a Ugandan reserve gently combing the tail of a red-tailed monkey, an interaction that contrasts with typical chimp aggression. Similar gentle contacts have been recorded in other primates, including a macaque forming an attachment to a chicken and a female gibbon stroking a mouse. Lead author Cyril Grueter, an associate professor of primatology at the University of Oxford, notes that such behaviors resemble the early stages of pet-keeping observed in humans.

Oxford primate study reveals monkeys nurture pets across species

The findings support the idea that the desire to care for non-human companions may extend back to a common primate ancestor. Behavioral ecologist Zoë Goldsborough of the Max Planck Institute of Animal Behavior remarks that theories link pet-keeping to either utilitarian functions such as hunting and protection or to an innate tendency for cross-species bonding. Psychologist Hal Herzog of Western Carolina University adds that allocating resources to unrelated species appears evolutionarily puzzling, underscoring the need for deeper evolutionary explanations.

New York Times

Grueter’s team compiled 427 documented instances of inter-species interaction across 88 primate species by reviewing media reports, scientific literature, and surveying primatologists. The catalog includes contacts with lizards, birds, deer, dogs, squirrels, and other mammals. The most frequent behaviors were playing together and grooming, suggesting that such interactions are widespread rather than isolated curiosities.

Oxford primate study reveals monkeys nurture pets across species New York Times

Researchers not involved in the study emphasize that while these observations are intriguing, systematic scientific analysis of inter-species care remains limited. Grueter argues that cataloguing these cases can provide clues to why humans keep pets, but he cautions that the phenomenon’s adaptive value is still unclear.

Oxford primate study reveals monkeys nurture pets across species

• “Lavishing resources on members of other species we have no evolutionary stake in seems to make no evolutionary sense,” — Hal Herzog, a psychologist and animal expert at Western Carolina University

New York Times

• “There are theories that pet-keeping began either because animals were useful for tasks like hunting and protection or because humans have a natural tendency to care for and bond with other living beings,” — Zoë Goldsborough, a behavioral ecologist at the Max Planck Institute of Animal Behavior

New York Times

• “The gibbon took very good care of the mouse,” — Cyril Grueter, lead author

Oxford primate study reveals monkeys nurture pets across species