Chimpanzees use insects to treat wounds, help each other - study

The research reveals the intelligence of chimpanzees and their prosocial behavior, highlighting how close they are to humans on the evolutionary ladder.

 A chimpanzee. One of the closest animals to humans on the evolutionary ladder (illustrative). (photo credit: Tambako The Jaguar/Flickr)
A chimpanzee. One of the closest animals to humans on the evolutionary ladder (illustrative).
(photo credit: Tambako The Jaguar/Flickr)

Humans are not the only animals to practice self-medication, with many others practicing it to some extent. But while this normally means eating things to fight sickness and parasites, it does not refer to treating open wounds with insects.

But chimpanzees seem to be able to do just that, applying insects to their wounds in order to treat them, a new study has found.

The research was undertaken at the Loango National Park in Gabon by researchers from Osnabrück University and the Ozouga Chimpanzee Project, and the findings were published in the peer-reviewed academic journal Current Biology

How did it work?

Over a 15-month period, the scientists observed 76 different open wounds on 22 different individual chimpanzees. In 19 different events, the chimpanzees began applying insects to these wounds.

This was done in the following steps:

  • Catch an insect
  • Place and squeeze the insect between their lips to immobilize it
  • Put the insect on the wound and move it around using lips or fingers
  • Remove the insect
  • Last two steps repeated if necessary

How did the scientists get the idea to even do this study?

The Ozouga Chimpanzee Project had already been studying this particular group of chimpanzees for seven years. However, in November 2019, volunteer Alessandra Mascaro saw something she hadn't ever seen before.

One of the chimpanzees, Sia, had an open wound on his foot. His mother, Suzee, was inspecting it and then suddenly caught an insect in the air and applied it to the wound.

The entire encounter was recorded on video.

“In the video, you can see that Suzee is first looking at the foot of her son, and then it’s as if she is thinking, ‘What could I do?’ and then she looks up, sees the insect, and catches it for her son,” Mascaro, who was the lead author of the study, said in a statement.

This was what inspired them to begin monitoring the group further for this behavior.

Is this really that impressive?

Yes. Most assume that animals don't normally use medicine to treat wounds or sickness, although it does in fact happen more than many realize.

Indeed, bears and elephants are both known to practice self-medicating. Even chimpanzees and bonobos, the primates most closely related to humans, are also already known to have practiced self-medication.

Further, the idea of tool use, which the concept of treating sickness could fall under as it involves applying a treatment to a wound rather than just eating something, is also far from unique to humans. Elephants, parrots, otters and, of course, chimpanzees and other primates are all known to be capable of tool use, to some extent. 

However, there are two things that stand out about this particular case.

First, there is the fact that chimpanzees are using insects to treat open wounds. 

Normally, when animals self-medicate, they do so by consuming certain substances like parts of plants. These usually have no nutritional value for them, hence why they aren't considered food, but they are suitable for dealing with internal issues, namely intestinal parasites.

There have also been studies documenting self-medication through a different method, applying plants or even arthropods to the fur or skin to fight parasites or treat diseases. For example, in 2017, a study published in the peer-reviewed journal Scientific Reports observed orangutans use leaves from the plant Dracaena cantleyi on their skin. This plant has noted anti-inflammatory properties and is also used by the indigenous human population in the same area as a treatment for body pain. 

But using insects to treat open wounds was something unseen before.

The implications of this are that the chimpanzees may know this treatment is effective, and thus know properties about these insects.

This is especially notable, as the researchers still have no idea which insects are being used or what medicinal properties they may even have.

The second thing that stands out from this discovery is that the chimpanzees weren't only treating themselves – they're treating each other.

This itself is unusual, as this sort of medicinal treatment isn't normally seen being practiced by animals to other animals.

This, the researchers argue, is an example of prosocial behavior, which means that rather than acting purely for one's own survival, the chimpanzees are acting in the interests of others.

“This is, for me, especially breathtaking because so many people doubt prosocial abilities in other animals,” explained co-author Simone Pika, an Osnabrück University cognitive biologist. 

“Suddenly we have a species where we really see individuals caring for others.”

The fact that chimpanzees practice prosocial behavior is reflective of how close they are to humans genetically. Indeed, as documented by expert Jane Goodall, chimpanzees not only share 99% of their DNA with humans, but they also engage in human-like behavior such as using and sharing tools, hunting in groups, using body language to communicate a wide range of emotions and messages.

Even their brains are structurally identical – though human brains are larger – meaning they are capable of logic, generalizing and abstract thinking.

The closest Great Ape species to humans are the chimpanzee and bonobo – both grouped under the genus Pan – were once thought to be the same species but are now recognized to be two distinct species in their own right, thought to have separated 1.5-2 million years ago, possibly because the group was split due to the formation of the Congo River.

While bonobos tend to be more mild-mannered than chimpanzees, and aggressive conflicts between them are rare, the starkest contrast between the groups is the fact that bonobos exist in a matriarchal social structure, but chimpanzees, like the remainder of Great Apes, are a patriarchal society.

They are also capable of being territorial and have even been documented going to war. 

The Gombe Chimpanzee War was a violent conflict between two communities of chimpanzees in Gombe Stream National Park in Tanzania between 1974 and 1978. The two groups were once unified in the Kasakela community but by 1974 the group started splintering into factions, as noted by Goodall. 

Over a span of eight months, a group of chimpanzees consisting of six adult males, three adult females and their offspring, separated themselves into the southern area of Kasekela, leaving behind eight adult males, twelve adult females and their young.

During the four-year conflict that ensued, all the males in the southern community were killed, disbanding their faction. The victors then tried to expand their territory but were driven out by yet another faction of chimpanzees at a later date.

The fact that such conflict among chimpanzees is possible, despite war being long thought of as something exclusively human, is just another major highlight of the similarities between the two primate species.

This, too, is the case with using insects to treat wounds and prosocial behavior, As such, the findings of studies like this help illustrate another way chimpanzees are more intelligent and social than many assume, and just how close they are to humans. And by understanding that, we can understand more about how our own cognitive functions have evolved over time in the course of evolution.

Shira Silkoff contributed to this report.