Chimpanzees Regularly Capture Insects and Apply Them onto Wounds

In a new paper published this week in the journal Current Biology, University of Osnabrück’s Dr. Simone Pika and colleagues report the first observations of chimpanzees applying insects to their own open wounds and to the wounds of conspecifics.

“Self-medication — where individuals use plant-parts or non-nutritional substances to combat pathogens or parasites — has been observed across multiple animal species including insects, reptiles, birds and mammals,” said Dr. Pika, a cognitive biologist with the Institute of Cognitive Science at the University of Osnabrück.

“Our two closest living relatives, chimpanzees and bonobos, for instance, swallow leaves of plants with anthelmintic properties and chew bitter leaves that have chemical properties to kill intestinal parasites.”

“However, despite research spanning decades from other long-term field sites in west and east Africa, external application of animal matter on open wounds has, until now, never been documented.”

“Our observations provide the first evidence that chimpanzees regularly capture insects and apply them onto open wounds,” said Dr. Tobias Deschner, a primatologist with the Institute of Cognitive Science at the University of Osnabrück.

“We now aim to investigate the potential beneficial consequences of such a surprising behavior.”

In November 2019, Alessandra Mascaro, an evolutionary biologist with the Max Planck Institute for Evolutionary Anthropology and a volunteer at the Ozouga Chimpanzee Project, observed a chimpanzee named Suzee inspecting a wound on the foot of her adolescent son, Sia, catching an insect out of the air, putting it into her mouth, and then applying it onto the wound.

The Ozouga Chimpanzee Project team members had been studying this group of chimpanzees in Loango National Park in Gabon, West Africa, for 7 years but hadn’t witnessed behavior like this before.

“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 said.

The team started to monitor the chimpanzees for this type of wound-tending behavior, and over the next 15 months (from November 2019 until February 2021) documented 76 cases of the group applying insects to wounds on themselves and others (eleven adult males, two adolescent males, one juvenile male, four adult females, two adolescent females, and two juvenile females).

“In 19 events, individuals (five adult males, one adult female, one juvenile female) applied an insect to one of their own wounds using the following behavioral sequence,” the authors said.

“First, they caught an insect; second, they immobilized it by placing and/or squeezing the insect between their lips; third, they placed the insect to an exposed surface of the wound and moved the insect on the surface using their fingertips or lips; fourth, they extracted the insect from the wound with the mouth or their fingers. Steps three and four are often repeated multiple times during each event.”

“Though the insect species utilized have not yet been identified, there are several consistencies across all our observations: they appear to be winged, flying insects, given the fast motion used to catch them; the insects are caught from under a leaf or branch; they are 5 mm in size and usually dark in color and there was no observation of insect ingestion.”

They theorize that the insects might have soothing properties that could provide pain relief.

“Studying great apes in their natural environments is crucial to shed light on our own cognitive evolution,” Dr. Deschner said.

“We need to still put much more effort into studying and protecting them and also protecting their natural habitats.”

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Alessandra Mascaro et al. 2022. Application of insects to wounds of self and others by chimpanzees in the wild. Current Biology 32 (3): PR112-R113; doi: 10.1016/j.cub.2021.12.045