New discovery reveals chimpanzees in Uganda use flying insects to tend their wounds

Animals respond to injury in many ways. So far, evidence for animals tending wounds with biologically active materials is rare. Yet, a recent study of an orangutan treating a wound with a medicinal plant provides a promising lead.

Chimpanzees, for example, are known to lick their wounds and sometimes press leaves onto them, but these behaviours are still only partly understood. We still do not know how often these actions occur, whether they are deliberate, or how inventive chimpanzees can be when responding to wounds.

Recent field observations in Uganda, east Africa, are now revealing intriguing insights into how these animals cope with wounds.

Read more: Inside the chimpanzee medicine cabinet: we've found a new way chimps treat wounds with plants

As a primatologist, I am fascinated by the cognitive and social lives of chimpanzees, and by what sickness-related behaviours can reveal about the evolutionary origins of care and empathy in people. Chimpanzees are among our closest living relatives, and we can learn so much about ourselves through understanding them.

In our research based in Kibale National Park, Uganda, chimpanzees have been seen applying insects to their own open wounds on five occasions, and in one case to another individual.

Behaviours like insect application show that chimpanzees are not passive when wounded. They experiment with their environment, sometimes alone and occasionally with others. While we should not jump too quickly to call this “medicine”, it does show that they are capable of responding to wounds in inventive and sometimes cooperative ways.

Each new insight adds reveals more about chimpanzees, offering glimpses into the shared evolutionary roots of our own responses to injury and caregiving instincts.

First catch your insect

We saw the insect applications by chance while observing and recording their behaviour in the forest, but paid special attention to chimpanzees with open wounds.

In all observed cases, the sequence of actions seemed deliberate. A chimpanzee caught an unidentified flying insect, immobilised it between lips or fingers, and pressed it directly onto an open wound. The same insect was sometimes reapplied several times, occasionally after being held briefly in the mouth, before being discarded. Other chimpanzees occasionally watched the process closely, seemingly with curiosity.

Most often the behaviour was directed at the chimpanzee’s own open wound. However, in one rare instance, an adolescent female applied an insect to her brother’s wound. A study on the same community has shown that chimpanzees also dab the wounds of unrelated members with leaves, prompting the question of whether insect application of these chimpanzees, too, might extend beyond family members. Acts of care, whether directed towards family or others, can reveal the early foundations of empathy and cooperation.

The observed sequence closely resembles the insect applications seen in Central chimpanzees in Gabon, Africa. The similarity suggests that insect application may represent a more widespread behaviour performed by chimpanzee than previously recognised.

Read more: A chimpanzee cultural collapse is underway, and it's driven by humans

The finding from Kibale National Park broadens our view of how chimpanzees respond to wounds. Rather than leaving wounds unattended, they sometimes act in ways that appear deliberate and targeted.

Chimpanzee first aid?

The obvious question is what function this behaviour might serve. We know that chimpanzees deliberately use plants in ways that can improve their health: swallowing rough leaves that help expel intestinal parasites or chewing bitter shoots with possible anti-parasitic effects.

Insects, however, are a different matter. Pressing insects onto wounds has not yet been shown to speed up healing or reduce infection. Many insects do produce antimicrobial or anti-inflammatory substances, so the possibility is there, but scientific testing is still needed.

For now, what we can say is that the behaviour appears to be targeted, patterned and deliberate. The single case of an insect being applied to another individual is especially intriguing. Chimpanzees are highly social animals, but active helping is relatively rare. Alongside well-known behaviours such as grooming, food sharing, and support in fights, applying an insect to a sibling’s wound hints at another form of care, one that goes beyond maintaining relationships to possibly improving the other’s physical condition.

Big questions

This behaviour leaves us with some big questions. If insect application proves medicative, it could explain why chimpanzees do it. This in turn raises the question of how the behaviour arises in the first place: do chimpanzees learn it by observing others, or does it emerge more spontaneously? From there arises the question of selectivity – are they choosing particular flying insects, and if so, do others in the group learn to select the same ones?

In human traditional medicine (entomotherapy), flying insects such as honeybees and blowflies are valued for their antimicrobial or anti-inflammatory effects. Whether the insects applied by chimpanzees provide similar benefits is still to be investigated.

Finally, if chimpanzees are indeed applying insects with medicinal value and sometimes placing them on the wounds of others, this could represent active helping and even prosocial behaviour. (The term is used to describe behaviours that benefit others rather than the individual performing them.)

Watching chimpanzees in Kibale National Park immobilise a flying insect and gently press it onto an open wound reminds us how much there is still to learn about their abilities. It also adds to the growing evidence that the roots of care and healing behaviours extend much further back in evolutionary time.

If insect applications prove to be medicinal, this adds to the importance of safeguarding chimpanzees and their habitats. In turn, these habitats protect the insects that can contribute to chimpanzee well-being.

Kayla Kolff received funding from the German Research Foundation (DFG), project number 274877981 (GRK-2185/1: DFG Research Training Group Situated Cognition).