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This behavior of one animal applying medication to the wounds of another has never been observed before, and it may be a sign of helpful tendencies in chimpanzees similar to empathy in humans, according to a new study.
Bears, elephants and even bees have been known to self-medicate against parasites and illness.
“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 Pika, study author and professor of comparative biocognition, at the University of Osnabrück’s Institute of Cognitive Science in Germany, in a statement.
“Our two closest living relatives, chimpanzees and bonobos, for instance, swallow leaves of plants with anthelmintic (antiparasitic) properties and chew bitter leaves that have chemical properties to kill intestinal parasites.”
But this is the first recorded instance of animals applying other animal matter — the insects — to open wounds.
“Chimpanzees eat insects but we did not know that they catch and use them to treat their wounds,” Pika said. “Hence, they not only have an understanding of their food species (plants, insects, monkeys, birds, reptiles) but probably also about characteristics of other animal species that help to act against injuries.”
Care in a chimpanzee community
The discovery was initially made when project volunteer Alessandra Mascaro watched an interaction between a mother chimp, Suzee, and her son Sia, in 2019. Sia had an injured foot, and Suzee appeared to be tending to it.
“I noticed that she appeared to have something between her lips that she then applied to the wound on Sia’s foot,” Mascaro said in a statement. “Later that evening, I re-watched my videos and saw that Suzee had first reached out to catch something which she put between her lips and then directly onto the open wound on Sia’s foot.”
About a week later, it happened again when doctoral student Lara Southern watched adult male chimp Freddy doing something similar. The team surmised that the chimps were capturing tiny flying insects from the air.
Over the next year, the researchers closely watched and filmed all of the chimps that showed signs of injury and recorded 22 chimps applying insects to their own wounds.
Then, Southern witnessed chimps tending to each other.
“An adult male, Littlegrey, had a deep open wound on his shin, and Carol, an adult female, who had been grooming him, suddenly reached out to catch an insect,” Southern said in a statement. “What struck me most was that she handed it to Littlegrey, he applied it to his wound and subsequently Carol and two other adult chimpanzees also touched the wound and moved the insect on it. The three unrelated chimpanzees seemed to perform these behaviours solely for the benefit of their group member.”
This happened again when another adult male also tended to Littlegrey’s thumb about four months later.
The team cataloged 76 cases of chimps using insects on their wounds and the wounds of others over 15 months, from November 2019 to February 2021.
Helping one another
Tending to others is prosocial, or positive behavior that is in the interest of helping others — something that isn’t often observed in animals.
“This is, for me, especially breathtaking because so many people doubt prosocial abilities in other animals,” Pika said. “Suddenly we have a species where we really see individuals caring for others.”
“Prosocial behaviours have long posed a problem for evolutionary theory, because it was not immediately clear why organisms might help others in the face of selection operating in the interest of self,” the authors wrote in the study.
It’s difficult to say if what the chimps are doing is motivated by empathy, but the researchers were surprised to see that the chimps recognized that how they treat their own wounds can be applied to others and helped one another even if they weren’t related.
“We do not know whether the observed behavior involves empathy,” Pika said. “We know that it may qualify as prosocial behaviour, meaning it may increase the welfare of another animal — feeling better via the social attention and caring, or via substances in the saliva-insect mix that may be soothing or anti-inflammatory. There are examples of chimpanzees adopting and rescuing other chimpanzees, which may involve empathy.”
Chimpanzees have long shown that they benefit from cooperation when taking on activities like territorial patrols or hunting, but researchers remain divided on if chimpanzees can be considered proscial or empathetic.
“Our observations may add another facet to the ongoing debate on prosocial behaviors and inspire future studies investigating the behaviours surrounding wound care and the potential medicative function of insect-application,” the authors wrote in the study.
It’s possible that the insects the chimps are using have antiseptic or anti-inflammatory properties to soothe the pain of their injuries and promote healing. There is a long history of humans using insects for these same purposes dating back to 1,400 BC, the researchers said. They also can’t rule out that this is potentially more of a placebo effect.
Previous research has shown that some behaviors in chimpanzees, like using tools, is a learned behavior. Perhaps medicating and helping others is one of those practices passed among the group, too.
Next, the Ozouga researchers wants to identify the insects the chimps are using and closely follow which of the animals seem motivated to help others in their community. They also want to study the insects to see if they have any pharmaceutical properties and determine if the use of the insects helped heal the wounds.
“It is just fascinating to see that after decades of research on wild chimpanzees they still surprise us with unexpected new behaviours,” Deschner said in a statement. “Our study shows that there is still a lot to explore and discover about our closest living relatives, and we therefore need to still put much more effort into protecting them in their natural habitat.”