In a nature reserve in Gabon, Africa, German scientists have seen chimpanzees rubbing insects in open wounds on themselves and others of their own kind.

Playing doctor is not reserved for people: animals also undergo all kinds of treatments. For example, there are capuchin monkeys that protect themselves against mosquitoes by to smear with the poison of millipedes and ants that process resin in their nests to repel microbes and fungi. Now chimpanzees – at least a number of specimens belonging to a group in Gabon – appear to treat their wounds with insects.

helping others

Biologist Alessandra Mascaro of the Max Planck Institute for Evolutionary Anthropology in Leipzig was the first to observe this unusual behaviour. In 2019, she saw the female chimpanzee Suzee (pictured left) rubbing an insect in a wound on her son Sia’s foot.

She and colleagues recorded the same behavior 21 more times in the following months, the researchers wrote in the scientific journal. Current Biology† In most cases, these involved chimpanzees who treated their own wounds. In a few cases, like Suzee, they helped another.

The treatment proceeded as follows. First, the animals caught an insect that they clamped between their lips. Then they place that on the open wound, where they move it back and forth with their lips or fingers.

Tunnel vision

Jaap de Roode, an expert on animal self-medication at Emory University in the US, calls it an “interesting observation.” “A strong point of this study is that the researchers have seen the behavior in many different chimpanzees in a short time.”

However, this raises the question of why the behavior has never been observed before. This can have two causes, says De Roode. “First, it may be a relatively new phenomenon. One monkey invented it, others then imitated it. Second, scientists sometimes suffer from tunnel vision. Then they study animals for a specific purpose and don’t see other things.”

Simone Pika, one of the researchers involved in the study, endorses the latter. “We all have our scientific ‘curtains’, which the younger generation has to open for us from time to time. It is very well possible that other researchers reading our article will now see similar behavior in the chimpanzees they study.”

Does it work?

An important point is that the researchers do not yet know which insects are involved. The scientists don’t get much further than they can fly, are about half an inch long and are usually dark in color.

It is also not known whether the treatment actually works. “That’s actually the biggest question,” says De Roode. “Do those wounds actually get better, or is it a purely cultural phenomenon?”

Pika announces that Mascaro, who was the first to observe the behavior, will now tackle this question as a PhD student. “We are very curious about which insects the chimpanzees use and which substances they contain.”