It was supposed to be a routine observation. Alessandra Mascaro was studying her favorite chimpanzee, a juvenile male named Sia, when she first noticed some strange behavior. Sia’s mother, Suzee, plucked something off of a leaf and rubbed it into a cut on Sia’s foot. Mascaro recorded the incident on video and shared it with her peers. Soon, similar observations flooded in from other scientists, volunteers, and field guides at the Loango Chimpanzee Project. It turned out these small specks were insects — and the primates seemed to be using them to treat wounds.
Humans aren’t the only animals that get sick and we are not the only ones that play doctor, either. In fact, scientists have documented “self-medicating” behaviors in the animal kingdom before. The never-before documented chimpanzee behavior captured by Mascaro is not only expanding our understanding of nature’s first aid but also demonstrating empathy may not be exclusive to humans.
What’s New — In a study published this week in the journal Current Biology, primatologists present evidence chimpanzees treat their own wounds and those of others with a mysterious insect. In previous studies, researchers have described mutual primate grooming and social fur rubbing, kind of like how you and a friend might apply sunscreen to each other’s backs.
Separately, scientists have noted the use of insects in fur-rubbing and other self-medicating behaviors. But the new study offers the first example of a wild animal treating another’s injury with an insect, says Mascaro.
“It’s incredible,” she adds. “We figured out that it was much more frequent than we’d expect. It’s just that before we never noticed.”
Scientists have documented medicinal behaviors in a range of animals. Birds build nests with antibacterial plants. Bees ward off hive fungus with natural resins. And many primates, from gorillas to capuchins, employ multiple types of self-treatment. For example, apes are known to eat rough leaves as a sort of laxative to get rid of intestinal parasites and monkeys have been observed rubbing plant material, ants, and millipedes into their fur to take advantage of chemicals that deter pests.
For the new study, Mascaro and her colleagues monitored a group of about 20 chimpanzees living in Gabon’s Loango National Park. From November 2019 to February 2021, they recorded multiple instances of chimps quickly swiping something out of the air or off leaves, placing it between their lips, and using their fingers or mouths to rub the unidentified, presumed insect over open cuts. The researchers noted 22 total instances of the odd behavior. In 19 cases the apes were attending to an injury on their own bodies but in three, an individual was treating another. Mascaro’s first mother-baby observation was the only one to involve clearly related apes.
Why It Matters — “No matter how intelligent we think that an animal is, they’re always showing us something more,” says Michael Huffman, a scientist at Kyoto University in Japan who was not involved in the new research. Though Huffman has spent decades studying animal self-medicating behavior, he says, “this is something different. I haven’t come across anything about topical application for open wounds.”
The findings suggest that chimpanzees have more ways of medicating than previously thought and that they may care for each other in unexpected ways. There’s long been disagreement about whether other primates are capable of empathy in the same way that humans are. Researchers have documented examples of empathy like contagious yawning in chimps and food sharing in bonobos. If chimpanzees tend to each other’s wounds that would be further evidence for positive, social tendencies.
“Our observations may add another facet to the ongoing debate,” Mascaro and her co-authors write in their newly published paper.
What’s Next — Though Huffman agrees that the social aspect of the behavior is interesting, he notes that more information is needed to verify the study authors’ inferences. “There were a few things that would really be nice for them to pursue in the future to make this a solid case.”
For example, the study researchers don’t know exactly how all the chimpanzees they observed are related. They only have information on mother-offspring relationships. It could be that all three observed instances of social wound care were between close relatives. In that case, there’d be an evolutionary benefit to the individuals providing care, because of shared genes, and empathy becomes a less likely explanation for the chimps’ actions. Further, three observations of social behavior aren’t very many.
Further, with the insect still unidentified, it’s impossible to know for sure if the observed behavior truly has medical value. Countless species thrive in the tropical environment, and researchers couldn’t just rush over to get a closer look at the insect — they maintain a distance of about 30 feet from the chimps while observing for the safety of the animals and themselves. But with more observations and insect sampling, identification is possible.
Mascaro hopes to collect and test the insects in future follow-up research to see if they contain any beneficial properties like antibacterial compounds. She’s already begun a new round of tracking injured chimps, following her subjects from when they wake up until they go to sleep for the night, to compare the recovery process of individuals who apply the insect method with those who don’t (similar to clinical trials in humans).
Huffman points out that if the unidentified insects do help heal wounds, it could offer insight into new human medical treatments. “Self-medication is perhaps one of the most direct contributions that animals have to make to us,” he says. “We still have so much to learn from them.”