Chimpanzee self-medicating

A Budongo chimpanzee feeding on the fruit of F. exasperate. (Credit: Elodie Freymann, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/))

Deep in the forests of Uganda, our closest living relatives may be practicing a sophisticated form of healthcare that has long eluded the notice of researchers. An extraordinary new study suggests that chimpanzees are not just passive consumers of their environment, but actively seek out plants with powerful medicinal properties to treat a variety of ailments.

Scientists from the University of Oxford and Neubrandenburg University of Applied Sciences have uncovered compelling evidence that chimpanzees in Uganda’s Budongo Forest are ingesting plants with strong antibacterial and anti-inflammatory effects. This discovery challenges our understanding of animal intelligence and could have far-reaching implications for human medicine.

The study, published in the journal PLOS ONE, examined 17 plant samples associated with unusual feeding behaviors in two chimpanzee communities. These behaviors included stripping bark, eating dead wood, and consuming specific plant parts that seemed to have little nutritional value. By combining behavioral observations, health monitoring, and rigorous pharmacological testing, the researchers were able to draw connections between the chimpanzees’ diet and potential medicinal benefits.

One of the most striking findings was the potent antibacterial activity of Khaya anthotheca, a tree species whose bark and resin were frequently targeted by chimpanzees, especially those with injuries or signs of infection. Extracts from this plant showed remarkable effectiveness against several bacterial strains, including some that are resistant to multiple drugs. This suggests that chimpanzees may be using K. anthotheca as a natural antibiotic.

Another fascinating discovery involved the fern Christella parasitica. This plant, rarely consumed by chimpanzees, was observed being eaten by an injured male. Laboratory tests later revealed that C. parasitica has powerful anti-inflammatory properties, suggesting its consumption may have been an attempt to reduce pain and swelling.

These findings paint a picture of chimpanzees as sophisticated foragers, capable of distinguishing between plants based on their medicinal properties. This behavior goes beyond simply eating nutritious foods and enters the realm of what researchers call “zoopharmacognosy,” or the study of how animals use plants for medicinal purposes.

Chimpanzee in a tree
Chimpanzees appear to be quite knowledgeable in the field of zoopharmacognosy. (Photo by Unsplash+ in collaboration with Getty Images)

How the Study Was Conducted

The research team employed a multi-faceted approach to investigate the potential medicinal properties of plants in chimpanzee diets. Their methodology can be broken down into several key components:

  1. Behavioral Observations: Researchers spent months observing two chimpanzee communities in the Budongo Forest, carefully documenting their feeding behaviors. They paid particular attention to unusual feeding events, such as bark stripping or the consumption of plants not typically part of the chimpanzees’ diet.
  2. Health Monitoring: The team collected fecal and urine samples from the chimpanzees to assess their health status. This included analyzing parasite loads and conducting urinalysis tests to detect signs of infection or other health issues.
  3. Plant Sample Collection: Based on their observations, the researchers collected samples from 13 plant species that were associated with unusual feeding behaviors or consumed by chimpanzees showing signs of illness.
  4. Laboratory Analysis: The plant samples were processed into extracts using different solvents to isolate various compounds. These extracts were then subjected to rigorous pharmacological testing.
  5. Antibacterial Assays: The extracts were tested against a panel of bacteria, including several drug-resistant strains, to assess their ability to inhibit bacterial growth.
  6. Anti-inflammatory Tests: The samples were also evaluated for their ability to inhibit COX-2, an enzyme involved in inflammation.

By combining these different approaches, the researchers were able to draw connections between the chimpanzees’ behavior, their health status, and the medicinal properties of the plants they consumed.

Key Results

The study’s findings were both extensive and intriguing. Here are some of the most significant results:

  1. Antibacterial Activity: Of the 51 plant extracts tested, 45 (88%) showed significant antibacterial activity against at least one bacterial strain. The most potent effects were observed with extracts from Khaya anthotheca bark and resin, and Alstonia boonei dead wood.
  2. Anti-inflammatory Effects: In the anti-inflammatory assays, 17 out of 51 extracts (33%) demonstrated strong COX-2 inhibition. The K. anthotheca bark and resin extract was particularly effective, showing even greater potency than some common over-the-counter anti-inflammatory drugs.
  3. Species-specific Effects: Different plant species showed varying levels of activity against different bacteria. For example, Syzygium guineense bark was effective against a wide range of bacterial strains, including some that are typically difficult to treat.
  4. Plant Part Differences: In cases where different parts of the same plant species were tested (e.g., bark vs. leaves), the researchers often found significant differences in bioactivity. This suggests that chimpanzees may be selectively targeting specific plant parts for their medicinal properties.
  5. Behavioral Correlations: The researchers observed several instances where chimpanzees with visible injuries or signs of illness sought out plants that later showed strong antibacterial or anti-inflammatory properties in laboratory tests.

These results provide compelling evidence that many of the plants consumed by Budongo chimpanzees have significant medicinal properties. Moreover, the behavioral observations suggest that the chimpanzees may be actively seeking out these plants for their health benefits.

Limitations of the Study

While the findings of this study are exciting, it’s important to acknowledge its limitations:

The study focused on a relatively small number of plant species and was limited to two chimpanzee communities. A broader investigation across more locations and plant species would be needed to generalize these findings.

The researchers also did not test plants that chimpanzees don’t consume, which would have provided a useful comparison to determine if the medicinal properties are unique to the selected plants.

Though likely a minor detail, the pharmacological tests were conducted in laboratory conditions, which may not perfectly reflect how these plant compounds would work in a living organism.

While the researchers collected some health data from the chimpanzees, more comprehensive and long-term health monitoring would be needed to definitively link plant consumption to health outcomes.

Finally, though the results suggest that chimpanzees may be selecting plants for medicinal purposes, it’s difficult to prove that this selection is intentional rather than instinctive or coincidental.

    Discussion and Implications

    This study opens up a fascinating new avenue of research at the intersection of primatology, ethnopharmacology, and medicine. The findings suggest that chimpanzees may possess a sophisticated understanding of their environment’s medicinal resources, challenging our perceptions of animal intelligence and self-awareness.

    From a conservation perspective, these results underscore the importance of preserving not just chimpanzee populations, but also their habitats. The forest isn’t just a source of food for these animals; it may also be their pharmacy. This adds another layer to the urgency of protecting these ecosystems.

    For human medicine, this research could point the way to new drug discoveries. Many of the plants tested showed potent effects against drug-resistant bacteria, a growing concern in modern healthcare. By following the “prescriptions” of our primate cousins, we may find new weapons in the fight against antibiotic-resistant infections.

    The study also highlights the value of interdisciplinary research. By combining behavioral observations, health monitoring, and pharmacological testing, the researchers were able to paint a much more comprehensive picture than any single approach could have provided.

    Looking forward, this study opens up numerous avenues for future research. Long-term studies tracking individual chimpanzees’ health and plant consumption could provide more definitive evidence of intentional self-medication. Broader surveys across different chimpanzee populations and habitats could reveal how widespread these behaviors are and how they might vary in different environments.

    In fact, one study earlier this year documented an orangutan that medicated itself with plants after suffering a facial wound.

    Ultimately, this research reminds us that there is still much to learn from the natural world. As we face growing health challenges, from antibiotic resistance to chronic inflammation, the solution might be growing in the forests, waiting to be discovered. That is, if we’re willing to learn from our primate relatives.

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