Chimps sometimes care for others' wounds, and scientists want to know why

Washington Post

14-05-2025

Primatologist Elodie Freymann arrived in Uganda's Budongo Forest in 2021 to observe the chimpanzees there and learn more about their ability to self-medicate with healing plants.
But as she flipped through a field book at the site containing the observations of researchers dating back to 1993, she began to notice accounts of the chimps not just ingesting plants to self-medicate, but using them for wound care — and sometimes not always on themselves.
In looking through 30 years of observations — as well as eight months of their own — Freymann and her colleagues found that the chimpanzees of Budongo have, in dozens of instances, administered first aid on themselves and others. According to Freymann, these observations, published Wednesday in Frontiers in Ecology and Evolution, raise questions over chimpanzees' capacity for empathy and altruism.
'It's hard to prove that a nonhuman animal has empathy because you can't sit down and have a conversation with them,' Freymann said. 'Most studies have been done in captivity. But this provides a case study, or several case studies, of chimpanzees in the wild possessing the ability to not just take care of themselves, but to transfer those skills to others.'
Chimpanzees and their behaviors have long dominated the field of zoopharmacognosy, the study of nonhuman self-medication. In addition to Freymann's previous research looking into chimpanzees ingesting healing plants to self-medicate, researchers who documented chimpanzees using insects to treat themselves and others in Loango National Park in Gabon argued that their behavior was evidence of their capacity for 'prosocial behaviors,' or voluntary actions that serve the best interest of another.
The research into the chimpanzees of Budongo found 34 instances of the chimpanzees practicing self-care, whether it be something as simple as licking their wounds or using leaves to wipe after a bowel movement or mating, to something more complex, such as chewing up plants and putting the material on a wound. There have been seven more instances of chimpanzees providing this sort of care on other chimpanzees and not just related kin.
In 2012, a subadult male — a chimpanzee between the age of 10 and 14 — identified as PS sucked the wound on the leg of another subadult male identified as ZG. In 2008, researchers documented an adult male identified as NK removing the nylon snare off an unrelated adult female.
The behavior also raises questions over whether the animals' caring skills are instinctual or acquired and then passed on through social learning, Freymann said. In 2008, researchers observed an adult female identified as NB, injured in a bout of intragroup aggression, applying a folded and chewed leaf to her wound. Her daughter, a juvenile female identified as NT, observed her mother doing this and then mimicked the behavior, chewing a leaf and then applying it to her mother's wound.
'I'm not making a case that every certain medicinal behavior is learned, but I think it's not out of the question that chimpanzees are capable of possessing medicinal culture,' she said.
Given that apes are considered the closest evolutionary cousin to human beings, understanding 'cognitive and social foundations of health-care behaviors in humans requires examining their evolutionary precursors in our closest living relatives,' Freymann argued in her research article. The chimpanzee behavior observed in Budongo suggests that 'the shared ancestors that we have with chimps and apes would have likely been capable of this kind of caregiving and have the capacity to identify those in need of care and to provide that to others,' Freymann said.
But Alexander Piel, a University College London associate professor of evolutionary anthropology who was not involved in Freymann's research, noted that the prosocial behavior demonstrated by chimpanzees in Budongo was very rare, which makes him reluctant to tie the findings to human evolution. There's always an inclination, he said, to connect similarities between humans and apes to evolution, and while it's always a possibility, 'we share other features with them, like our intense sociality, and we share them with non-apes.'
Researchers have observed prosocial health-care behaviors among non-ape species such as elephants and dwarf mongooses, Freymann wrote in her study. 'The fact that we see them in non-closely related species suggests that there are some other drivers to this beyond humanness or human-relatedness. … Empathy is a part of the equation, but the data doesn't support that it's the ultimate driver of this behavior,' Piel said.
The findings provide a good jumping-off point, Piel said, for exploration into the drivers behind this rare type of prosocial behavior — for example, why chimps are so selective in providing health care to other chimps. Freymann said there will be more studies to come, as well as more long-term monitoring.
'I think we're going to find medicinal cultures not just in chimps but in other animals as well,' Freymann said. 'There's debate always, but there are some medicinal behaviors that appear to be instinctual, the more basic ones. There are some behaviors that we've observed that I think are too complex to be instinctual.'