A chimpanzee was observed treating a companion’s wounds with medicinal plants. It did not discriminate between close relatives and those with no blood relation. Chimpanzees wiped their behinds with leaves after defecating and cleaned their genitals with leaves after mating. Previously, orangutans were also observed treating wounds with medicinal plants.
The observations of healing and hygiene behavior in primates closely related to humans are expected to help illuminate the origins of the medical system. In particular, the recent sighting of a chimpanzee treating a companion with no genetic relationship may serve as evidence for claims that altruistic behavior exists in non-human primates.
◇Emergency treatment with medicinal plants for injured companions
Dr. Elodie Freymann and her research team from the University of Oxford’s Department of Anthropology reported on the 15th in the international journal ‘Frontiers in Ecology and Evolution’ that they observed a chimpanzee in Uganda’s Budongo Forest treating the wounds of both itself and its companions with medicinal plants.
The research team studied the chimpanzee groups Sonso and Waibira in the Budongo Forest. Like other chimpanzees, they also engaged in fights or were injured in accidents. Many were injured by traps set by humans. Approximately 40% of the Sonso group sustained injuries from traps.
During a four-month observation period, 12 injury incidents occurred in the Sonso group, all presumed to result from conflicts within the group. In the Waibira group, one female was trapped in a snare, and four males were injured in fights.
The research team recorded a total of 41 care incidents. There were 34 cases of self-treatment and 7 cases of caring for companions. Dr. Freymann noted, “Chimpanzees removed foreign objects from wounds and licked them to apply the antibacterial components in their saliva, and they also crushed and chewed leaves to apply them.” All treated chimpanzees recovered.
◇Hygiene behavior of wiping with leaves also observed
The research team also observed hygiene behaviors performed by chimpanzees to prevent infection. After defecating, chimpanzees wiped themselves with leaves, just as early humans did. They were also observed wiping their genitals with leaves after mating.
Chimpanzees exhibited altruistic behavior. Among the 7 cases of caring for companions, there were 4 cases of wound treatment, 2 cases of removing snares, and 1 case of assisting with hygiene. The cases of caring for companions were not dependent on sex or age, and there were even 4 cases where individuals with no genetic relation within the group were cared for.
Until now, it was thought that social animals care for each other because it benefits the proliferation of offspring with similar genes. However, Dr. Freymann stated, “It appears that chimpanzees engage in intentional behaviors to recognize and alleviate the needs or suffering of other chimpanzees, even without direct genetic benefits.”
The sighting of primates self-treating is not unprecedented. Previously, in 2022, researchers from the Osnabrück University in Germany discovered that chimpanzees used insects to treat their own and their companions' wounds. Last year, researchers from the Max Planck Institute in Germany confirmed that Sumatran orangutans inhabiting Indonesian forests consumed herbs and applied crushed herbs to large wounds on their faces.
The researchers observed that chimpanzees also chewed medicinal plants to apply to their wounds and managed their hygiene by wiping with leaves after defecation or mating, demonstrating that the behaviors of healing and health management in primates are more widespread than previously thought. Freymann stated, “This research will not only illuminate the origins of the medical system but also impact claims that non-human animals exhibit empathy or altruism.”
References
Frontiers in Ecology and Evolution(2025), DOI: https://doi.org/10.3389/fevo.2025.1540922
Scientific Reports(2024), DOI: https://doi.org/10.1038/s41598-024-58988-7
Current Biology(2022), DOI: https://doi.org/10.1016/j.cub.2021.12.04