Chimpanzees rub insects on open wounds: Treating others may not be uniquely human

The chimpanzees of the Rekambo community in Gabon, West Africa never fail to surprise. For a start, they are known to kill and eat tortoises, which set them apart from any other community of chimpanzees. Now they have been seen displaying another unique behavior—one which has never been seen before despite many years of painstaking research.

In their new study published in the journal Current Biology, researchers have described how they saw Rekambo chimpanzees applying insects to their own open wounds, and, even more amazingly, to the wounds of other community members too.

Even by itself, treating wounds with insects is a groundbreaking observation—but until now no other animal, apart from humans, has been seen treating the wounds of others.

Humans have been using local remedies (such as roots, leaves, bark and other animals) as medicines for at least 5,000 years, a practice that has been passed down over generations within societies all over the world.

There is some use of insects in traditional human medicine too. For example, leeches have been used to clean wounds, slugs and snails to treat inflammation, spider webs to dress wounds and termite pincers to inject medicine under the skin.

Is it possible, perhaps, that such cultural use of plants and animals to treat injuries and illness was inherited from a common ape-like ancestor millions of years ago?

Self-medication in animals

As in humans, self-medication in wild animals is not uncommon –individuals from a diverse range of species, including chimpanzees, select particular plant foods that contain chemicals known to treat infection by parasites.

For example, caterpillars ingest plant toxins when infected by parasitic flies and gorillas consume a wide variety of plants that contain known compounds important in human traditional medicines.

Some species, such as wood ants, even anticipate infection, adding antimicrobial resin from nearby trees into their nests, which reduces the colony's exposure to microbes.

To date however, this widespread behavior almost always centers on self-medication with plant material. Never before has the use of insects on wounds been observed.

The groundbreaking chimpanzees

Over a 15-month period, beginning in November 2019, the team observed 76 open wounds on 22 different chimpanzees. There were 22 events of insect application by ten different chimpanzees. On 19 occasions, various individuals were seen applying an insect to one of their own wounds.

They caught an insect from the air, which they immobilized by squeezing between their lips. Then they placed it on an exposed surface of the wound and moved it around using their fingertips or lips. Finally, they extracted the insect from the wound.

But the use of insects didn't stop there. In a remarkable act of "allocare" (caring for another individual) a mother was seen applying insects to her offspring's wound, and a further two adult chimpanzees treated the wounds of another community member.