Chimpanzees Use Medicinal Plants to Treat Wounds

The line between human medical practices and animal instinct is becoming increasingly blurred. For decades, biologists believed that humans were the only species capable of diagnosing ailments and applying specific treatments. However, recent observations from the forests of Gabon and Uganda have shattered this assumption. Wild chimpanzees have been documented not only eating specific plants to cure internal parasites but also applying crushed insects and leaves to open wounds.

This behavior, known as zoopharmacognosy, suggests that our closest living relatives possess a form of folk medicine passed down through generations.

The Discovery at Loango National Park

The most striking evidence of wound treatment comes from the Ozouga Chimpanzee Project in Loango National Park, Gabon. Here, researchers observed a behavior never before seen in the animal kingdom: the topical application of insects to wounds.

The observation began when a volunteer, Alessandra Mascaro, watched a female chimpanzee named Suzee inspecting a wound on the foot of her adolescent son, Sia. Suzee suddenly snatched a flying insect from the air, immobilized it, and squeezed it between her lips. She then applied the crushed insect directly to the open wound on Sia’s foot.

This was not an isolated incident. Following this initial sighting, the team, led by cognitive biologist Simone Pika from the University of OsnabrĂĽck, documented 76 cases over a 15-month period involving 22 different chimpanzees.

The Process of Treatment

The application follows a distinct, methodical pattern that suggests intentionality rather than random behavior:

  1. Capture: The chimpanzee spots and catches a specific type of flying insect.
  2. Preparation: The insect is immobilized and placed in the mouth. The chimp squeezes it, likely to release bodily fluids or substances.
  3. Application: The crushed insect is pressed onto the wound.
  4. Maintenance: The chimp often uses a finger to move the insect around or cover the wound, similar to how a human might apply ointment.

While the specific species of insect has not yet been identified, researchers hypothesize that the insects contain antibiotic or antiviral properties that assist in healing or pain relief.

The Pharmacy of the Forest: Medicinal Plants

While the insect behavior is a recent discovery regarding topical treatment, chimpanzees have long been known to ingest plants for medicinal purposes. Recent studies in Uganda’s Kibale National Park and the Budongo Forest have provided concrete data on exactly what these apes are prescribing themselves.

Researchers, including Elodie Freymann from the University of Oxford, tracked sick chimpanzees to see what they ate compared to healthy group members. The sick animals sought out plants that were not part of their regular diet.

Specific Plants and Their Uses

The botanical knowledge displayed by these primates is specific and effective. Laboratory analysis of the plants selected by injured or sick chimps revealed that 88% of the samples inhibited bacterial growth.

  • Dead-Man’s Leaf (Alstonia boonei): A wounded chimpanzee was observed traveling specifically to eat the leaves of this tree. Lab tests confirmed the plant has strong antibiotic properties and is effective against Staphylococcus aureus, a bacteria known to cause skin infections.
  • Bitter Leaf (Vernonia amygdalina): Chimpanzees suffering from intestinal parasites strip the leaves and chew on the bitter pith. The juices contain sesquiterpene lactones, which kill parasites.
  • Christ’s Thorn (Scutia myrtina): Another plant sought by sick chimps, this was found to have antimicrobial properties that combat E. coli bacteria.
  • Whole Leaf Swallowing: Aside from chemical treatments, chimps use mechanical methods. They swallow rough, hairy leaves of the Aspilia plant whole. These leaves are not digested; instead, the microscopic hooks on the surface of the leaf act like Velcro, trapping worms in the digestive tract and dragging them out of the body.

Prosocial Behavior and Empathy

The most revolutionary aspect of the Loango observations is not just that chimps treat themselves, but that they treat others. In the animal kingdom, self-medication is rare but documented. However, medicating a peer is a clear sign of prosocial behavior.

In several documented instances, an adult female applied the insect treatment to another adult male who was unrelated to her. This challenges the long-held scientific view that non-human animals act solely out of self-interest or strictly for genetic offspring.

This suggests that chimpanzees possess:

  • Empathy: An understanding that another individual is in pain.
  • Knowledge Transfer: An understanding that a specific action (applying the insect) will alleviate that pain.

Cultural Transmission of Medical Knowledge

Biologists argue that this medical knowledge represents a culture. It is not an instinct written into their DNA. Instead, it is learned behavior. Young chimpanzees watch their mothers and other adults select specific leaves or catch specific insects. They mimic these actions until they master them.

This creates distinct “medical cultures” in different groups. Chimpanzees in Uganda might rely heavily on Alstonia boonei for infections, while the Loango group in Gabon relies on insect application. This variation mirrors human folk medicine, where treatments vary based on region and tradition.

Frequently Asked Questions

What kind of insects are the chimpanzees using? Researchers have not yet identified the specific species. The insects are flying arthropods, and the chimps move too quickly for samples to be collected easily. However, many insects produce antimicrobial substances to protect themselves, which the chimps are likely harvesting.

Do the treatments actually work? Laboratory tests on the plants used by chimps show high biological activity against bacteria and parasites. While we cannot clinically trial the “insect ointment” yet, the fact that the behavior persists across the group suggests it provides a tangible benefit, either in pain reduction or faster healing.

Do other animals use medicine? Yes. This field is called zoopharmacognosy. Bears apply osha root paste to fur to repel insects, and over 200 species of birds use “anting” (rubbing ants on feathers) to kill mites. However, the chimpanzee behavior is unique because they treat the wounds of others, not just themselves.

How does this help humans? This field leads to “bioprospecting.” By observing which plants animals use for healing, scientists can identify new compounds for human pharmaceuticals. Many plants used by chimps are also used by local human healers, confirming their medical validity.