Chimpanzees create and use tools, as we already know. But is it possible that they also use medication to treat their injuries? A new study suggests so.
Since 2005, researchers have studied a community of approximately 45 chimpanzees in Loango National Park, Gabon, on the west coast of Africa. Over a 15-month period, from November 2019 to February 2021, researchers noticed 76 open wounds in 22 chimpanzees. In 19 cases they saw one of them perform what appeared to be self-healing of the wound, using an insect as medicine. In some cases, one chimpanzee appeared to treat another. The scientists published their observations in the journal Current Biology on Monday (7).
The procedure was similar on all occasions. First, the chimpanzees caught a flying insect; then they immobilized him, pressing him between their lips. Then they placed the insect over the wound, moving it in a circle with their fingertips. Finally, they removed the insect, using their mouths or fingers. Often they would place the insect in the wound and take it out several times.
Researchers don’t know what insect the chimpanzees used, or exactly how it might help heal a wound. They know they were small, dark-colored flying insects. There is no evidence that chimpanzees eat the bugs — they certainly squeeze them between their lips and apply them to wounds.
There are other reports of self-medication in animals, including dogs and cats that eat grass or plants, presumably to make them vomit, and bears and deer that consume medicinal plants, apparently to self-medicate. Orangutans have been seen applying material to relieve muscle injuries. But researchers are unaware of previous reports of non-human mammals using insects for medicinal purposes.
In three cases, the researchers saw chimpanzees use the technique on another chimpanzee. In one, an adult female named Carol tended to a wound in the leg of an adult male, Littlegrey. She took an insect and gave it to Littlegrey, who placed it between his lips and applied it to the wound. Later, Carol and another adult male were seen rubbing the insect around Littlegrey’s wound. Another adult male approached, removed the insect from the wound, placed it between his lips and then reapplied it to Littlegrey’s leg.
An adult male chimpanzee named Freddy was a keen insect medicine enthusiast, treating injuries to his head, arms, back, left wrist, and penis several times. One day, researchers saw him treat the same arm wound twice. The researchers don’t know how Freddy was injured, but some cases likely involved fighting with other males.
Some animals cooperate with others in similar ways, according to Simone Pika, director of the animal cognition laboratory at the University of Osnabruck in Germany, who is one of the study’s authors. “But we don’t know of any other mammalian cases,” she said. “It could be an acquired behavior that only exists in this group. We don’t know if our chimpanzees are special in that sense.”
Aaron Sandel, an anthropologist at the University of Texas at Austin, found the work valuable, but at the same time expressed certain doubts. “They don’t offer an alternative explanation for the behavior, nor do they make a connection to what insect it might be,” he said. “The leap into a potential medical role is overkill at this point.”
But, he said, “caring for your own wounds or that of others using an instrument, another object, is very rare.” Documenting chimpanzees caring for others is “an important contribution to the study of the social behavior of monkeys,” added Sandel. “And it’s also interesting to ask if there’s empathy involved in that, like in humans.”
In some forms of monkey social behavior, it is clear that there is a valuable exchange. For example, combing another chimpanzee provides relief from the parasites for the combed animal, but also a snack of bugs for the combing animal. But in cases that Pika has observed, he said, the chimpanzee gets nothing in return. For her, this shows that monkeys are involved in an act that increases “the well-being of another being” and teaches us more about primate social relationships.
“With each field observation we learn more about chimpanzees,” she said. “They really surprise us.”
Translated by Luiz Roberto M. Gonçalves.
