# Monkeys Keeping Pets and Forming Cross-Species Friendships Primate interactions with other species shed light on the origins of human-animal bonds. - **Source:** [Scientific American Content: Global](https://brifing.si/source/4f066134-e06d-4415-87ef-305e3dc2aba6) - **Published:** 2026-08-08 - **Original article:** - **On Brifing:** https://brifing.si/s/f4c6d11a-c2c7-456e-b4f4-e7d01301aba0 ## The beginning of a surprising discovery At Shanghai Zoo, a white-cheeked gibbon was observed gently petting a mouse that entered its enclosure instead of eating it. This unexpected behavior caught primatologists' attention. Similar interactions were recorded when snub-nosed monkeys played with domestic pigs in southwestern China. These observations led to documenting 427 primate-species interaction cases since the 1970s. ## Scope of cross-species interactions The research revealed relationships between 88 primate species and 127 different animal species. Interactions included diverse species like sheep, deer, owls and lizards. While play and grooming were most common, food sharing and even infant adoption cases were recorded. Primates initiated 73% of the interactions. ## Japanese macaques' friendship with sika deer Long-term observations in Japan of macaques grooming and riding sika deer provide iconic examples of peaceful cross-species relationships. This behavior has continued for years, offering important clues about the evolutionary origins of social bonds. Similarly notable was a silverback gorilla carefully cradling a wild bushbaby. ## Young play, females care Clear age and gender differences emerged. While 68% of young primates played with other species, 82% of adult females engaged in grooming. This distribution matches traditional role divisions in primate societies. Juveniles develop motor skills while females extend caregiving instincts to other species. ## Evolutionary advantages of behaviors Grooming offers concrete benefits like parasite removal and hygiene maintenance. Play enhances cognitive flexibility and social skills. Cooperative foraging among different primate species in tropical forests shows ecological foundations. But some behaviors, like langurs stroking squirrels, stem from pure curiosity. ## The dark side: abuse and abduction Not all interactions were positive. In 15% of cases, primates abducted infants of other species; 7% involved violence. While some cases like a capuchin adopting a marmoset showed care, others documented monkeys roughly handling puppy dogs, revealing the complexity of cross-species relationships. ## Unusual friendships in zoos The 2017 case of macaque Niv adopting and caring for a chicken in an Israeli zoo proves these behaviors occur in human-controlled environments. Similar long-term relationships were recorded in 40% of captive primates, showing social flexibility isn't limited to natural habitats. ## Illuminating human-animal bond evolution This study reveals primates' cross-species social flexibility exceeds previous assumptions. It helps understand evolutionary origins of humans' unique relationships with other species. Increasing interspecies contact due to forest fragmentation suggests these behaviors may become more frequently observed. ## Sources covering this story - https://www.scientificamerican.com/article/monkeys-keep-pets-and-maintain-friendships-with-other-animals/ — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._