May 14, 2025, 12:36 pm | Read time: 6 minutes
Using leaves as toilet paper or pressing them on injuries—such behaviors seem surprisingly human. A new long-term study from Uganda reveals that chimpanzees use plant parts not only as hygiene items but also to provide medical care for themselves and others, even when they are not related. PETBOOK editor and biologist Saskia Schneider summarizes the fascinating findings.
It’s not new that apes use sticks as tools. Now, an international research team led by primatologist Dr. Cat Hobaiter from the University of St. Andrews has documented for the first time how chimpanzees use leaves and other plants for hygiene and wound care. The large-scale behavioral study primarily focused on how wild chimpanzees in the Budongo Forest (Uganda) deal with injuries. The findings were published in the journal “Frontiers in Ecology and Evolution.”
In analyzing data from over 30 years of observations of two chimpanzee communities (Sonso and Waibira), they noted not only wound care but also hygiene behaviors, such as wiping genitals. The truly exciting aspect was that the team scientifically documented health behaviors directed not only at themselves but also at others for the first time. The observations provide fascinating insights into the evolutionary origins of caregiving and medical behavior.
How Common Are Hygiene and Health Care Among Chimpanzees?
Medical behavior is by no means limited to humans. Many animal species practice so-called self-medication–such as by eating specific plants to combat parasites. In May 2024, a study found that an injured orangutan seemingly consciously created a remedy and treated its wound with it (PETBOOK reported).
It becomes particularly interesting when animals treat not only themselves but also others–so-called “prosocial” behaviors. Among chimpanzees, our closest living relatives, this is especially revealing because they live in complex social structures with changing group bonds. Until now, prosocial health behaviors like wound care among non-relatives were considered rare. The use of leaves and plant parts for hygiene by chimpanzees has also been scarcely documented scientifically.
In the current study, researchers aimed to determine how widespread these behaviors actually are–and whether they might be based on empathetic abilities.
What Was Studied–and How?
The study analyzed hygiene and health behavior in wild eastern chimpanzees in two groups in the Budongo Forest (Uganda): Sonso and Waibira. The data included:
- Long-term observations (1993–2024),
- Video material from the “Great Ape Dictionary” (over 13,800 clips),
- voluntary case reports via an online platform (CSMAS),
- and two new field phases of four months each of direct observation (2021 in Sonso, 2022 in Waibira).
They specifically documented self-directed and other-directed health behaviors–such as wound care, hygiene (e.g., genital cleaning with leaves), and the removal of wire snares (snare traps). Additionally, researchers collected plant samples and had them botanically identified to assess potential medicinal properties. All research was conducted with the approval of Ugandan authorities and in compliance with animal welfare field practices.
In Over 60 Percent of Health Behavior Cases, Chimpanzees Used Leaves and Other Plant Material
Overall, researchers documented 41 relevant health behaviors and 34 cases of self-care. About 62 percent of these behaviors involved plant material. The cases included:
- 23 wound treatments (e.g., licking wounds, applying chewed plant parts, leaf poultices),
- one successful snare removal, and
- ten hygienic behaviors like genital or anal cleaning with leaves.
The study also documented seven cases of care for group members. Chimpanzees treated others’ wounds by licking, applying saliva, or using plants–even among non-relatives. Researchers also observed three successful attempts to remove a wire snare from another chimpanzee’s body. Notably, hygienic behavior–such as genital cleaning after mating–was observed in one case with a conspecific.
Particularly remarkable: In several cases, chimpanzees used leaves from plant species known in traditional human medicine for their wound-healing, antibacterial, or anti-inflammatory properties–such as Niando (Alchornea floribunda), Acalypha sp., or Senna spectabilis.
Some Behaviors Could Be Based on Empathetic Perception
The study systematically shows for the first time that chimpanzees provide medical care not only to themselves but also to others–regardless of kinship. This indicates complex cognitive and social abilities in the animals. Particularly relevant is that some of these behaviors could be based on empathetic perception: Chimpanzees apparently recognize the pain and needs of others–and act accordingly, even when it poses risks to themselves (such as infection risk when licking wounds or removing dangerous wire snares).
The fact that some animals deliberately use plants with known medicinal properties suggests a sophisticated health knowledge. The combination of self-observation, experiential learning, and possibly social learning could contribute to the development of individual or group-specific healing strategies. The observation that such behaviors were also shown among non-relatives suggests that fundamental traits of care, compassion, and even altruism may be deeply rooted evolutionarily–and did not originate solely with humans.
Still Unclear How Widespread Prosocial Behavior Really Is
The study is the most comprehensive survey of health behavior in wild chimpanzees to date. However, there are limitations: No prosocial care actions were documented in the Waibira group. Essentially, this behavior was observed only once, when a chimpanzee used leaves to clean a conspecific’s genitals after mating. This does not mean that such behaviors are rare or infrequent, but likely reflects the lower observation density. Nevertheless, the small number of prosocial cases does not yet allow for generalizing statements about frequency or prevalence in species comparison.
The exact effects of the plants used were not tested in the lab–their medicinal significance is based on known pharmacological data and ethnomedicinal sources.
It also remains open to what extent the observed behaviors are passed on through social learning within the groups–whether there is something like medical “culture” among chimpanzees. Nevertheless, the study provides valuable foundations for further research–such as the role of empathy, social learning, and environmental factors in the development of caregiving behavior.
Orangutans Treat Their Wounds With Self-Made Remedy
Study shows gorillas use plants medicinally
Animals also mourn the loss of their own kind
Conclusion
This long-term study provides the most comprehensive overview to date of self-directed and other-directed medical behaviors in wild chimpanzees. The documented cases of wound treatment, hygiene behavior, and assistance with snare injuries show that caregiving among chimpanzees is not an exception–even toward non-relatives. These findings expand our understanding of empathy, altruism, and the evolutionary roots of human medicine.
The fact that chimpanzees deliberately use certain leaves and plant parts suggests remarkable health knowledge. Future research should clarify whether and how such behaviors are socially learned and culturally transmitted–and what role environmental factors play. For species conservation, the results also offer practical insights: By protecting the medicinal resources used and minimizing anthropogenic risks like snare hunting, we can actively contribute to the health and survival of these fascinating great apes.