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Natural History

Visual reports of my scientific adventures 

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Budongo Conservation Field Station (BCFS)
(June-October 2021 and 2022)

The ability to self-medicate is not unique to Homo sapiens. Over the last few decades, self-medication has been observed in a variety of primate and non-primate species and throughout several localities. Non-human self-medication takes many forms and involves a variety of medicinal resources. In chimpanzees, there are two well-established self-medicative behaviors. The first, called leaf swallowing, involves the ingestion of whole leaves with tiny, hook-like hairs. As the leaves pass through the gut, the hairs work like velcro, pulling intestinal endoparasites off the gut wall as they pass through the stomach - resulting in their expulsion. The second behavior, bitter-pith chewing, which specifically involves ingestion of the plant Vernonia amygdalina has only been observed in a site called Mahale in Tanzania. This behavior involves the stripping of pith from this species and the subsequent ingestion of the bitter juice and fibers. Individuals with high parasite loads observed engaging in this behavior were found to show a subsequent decrease in their internal parasite load. This is attributed to the strong bioactive properties of the compounds found in this plant's pith.

 

Beyond the two established behaviors, many other resources have been proposed as forms of therapeutic self-medication for non-human animals. However, as the burden of proof for establishing novel self-medicative resources is high, and these events are relatively rare in the wild, many proposed self-medicative resources remain unproven.

My PhD project, titled ‘Self-Medication in Budongo Forest Chimpanzees: Investigating the Use of Putative Self-Medicative Resources in the Sonso and Waibira Communities', aimed to advance our understanding of chimpanzee self-medication with a focus on two wild chimpanzee populations living in Budongo Forest, Uganda. To conduct my research, I travelled to Uganda for two extended stays. Across these field seasons, I spent 8.5 months in the forest, collecting behavioral, health, and ecological data. From there, I travelled to Germany to pharmacologically test 17 suspect plant samples I had observed ill or wounded chimpanzees consuming. Back at the University of Oxford, I sorted through and analyzed my data, which revealed several novel results and insights.

 

Throughout my time in the forest, I documented as much as I could about my surroundings and the flora and fauna of Budongo. Inspired by naturalists like Alexander Humboldt, Maria Sybilla Marion, and Anna Atkins, I attempted to take a natural historical approach to my research, drawing, photographing, and writing as much as I could about my time in the field. Below I've attempted to provide a small window into the forest and share some of my thoughts on the important implications of this topic for conservation. 

Click below to hear some sounds of Budongo Forest.

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Sounds of BudongoEF
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A Day in the Life at BCFS

A Day in the Life at BCFS

A short film documenting my daily routine during my time in Budongo (shot by Austen Deery).

 

 

 

I began my DPhil in evolutionary anthropology at the University of Oxford a year into the Covid-19 pandemic. As the virus raged across the globe, fieldwork seemed off the table. When a spot opened at the Budongo Conservation Field Station, I only had a few weeks to prepare, gathering supplies, writing grants, and learning as much as I could about the flora and fauna of the forest which I would soon call home. No matter how much I read, or how many hours I spent on Google Earth, I could not picture life in Budongo.

 

I first set off for fieldwork in June 2021 to begin my study on chimpanzee self-medication. Although there were many angles from which I could have approached this question, one particular behavior had caught my attention—chimpanzee bark stripping. Bark stripping, which is not unique to chimpanzees, involves the peeling of bark from the trunks and buttresses of trees, and subsequently ingesting the cambium—the layer between the xylem (wood) and phloem (bast) tissues. This behavior leaves distinctive wounds on the tree’s lower trunk which eventually heals over, leaving subtle scarring. As bark stripping seemingly offers little nutritious value, is energy-intensive, and is only rarely observed, I wondered if perhaps chimpanzees may be using certain barks as medicines—exploiting the bioactive properties that are present in certain trees. I arrived in Budongo, equipped with binoculars, an iPad, a GPS, fecal collecting tubes, and botanical collecting equipment—ready to study whether Budongo chimpanzees could be using the forest as their pharmacy, and if so, which trees may play a critical role in their survival.

Medicinal Trees

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Behavioral Data Collection

In the behavioral data collection phase of my PhD project, our days began before the sun had risen. Each morning, myself and a staff-primatologist colleague, ventured into the forest to locate the chimpanzees. My first year I worked with BCFS veteran Geresomu Muhumuza, who has worked at the station for over 30 years, and who patiently taught me the names of each chimpanzee and how to identify the forest's many trees. The second year I partnered with Eguma Robert Yikii, whose background in forestry made him an expert in many of the medicinal trees I was studying.

 

Clad in big rubber rain boots, we navigated through clay pits, across rivers, and over steep hills, surrounded on all sides by the calls of birds and the hum of bugs. We employed various methods to find them, such as listening for their morning calls or returning to where we had last seen them. Often, we headed to known feeding trees that were currently fruiting, as these were likely spots to find them eating breakfast. Once we identified a focal chimpanzee, our day involved following them wherever they led us. Throughout this process, I meticulously documented their actions, including everything they ate and did,  using my iPad. I also kept a detailed field notebook for noteworthy observations. 

Days in the forest could differ greatly from one another. From sudden rainstorms to sweltering afternoons, the weather was often variable and hard to predict. Some days the chimpanzees were active, requiring us to run through dense parts of the forest, tripping over roots and ducking under vines. On other days the group was more sedentary, preferring to spend their afternoon feeding, grooming, or resting. These calm moments were often times of introspection, when I could lean against a tree and just watch them without having to write or record - and it was on these quiet days that the other forest inhabitants would reveal themselves. From chameleons and rhino vipers, to red-tailed monkeys and guinea fowl, the forest was teeming with animal life.

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Health Monitoring

In my PhD research, we implemented a daily health monitoring protocol for the chimpanzee community. Our primary objective was to maintain a comprehensive record of the health status of individual chimpanzees, allowing us to identify those potentially unwell and more likely to engage in self-medication behaviors. To do this, we systematically collected dung and urine samples and subjected them to a battery of tests for various pathogens and parasites. At the conclusion of each day, my colleague, Daniel Sempebwa,  microscopically analyzed these samples in his lab to identify any internal parasites present in the chimpanzees. This approach enabled us to not only track the health of each chimpanzee within the group but also to gain valuable insights into the overall health and well-being of the entire community.

Botanical Collecting

When I encountered instances of chimpanzees consuming unconventional or atypical food sources, particularly in cases involving sick or injured chimpanzees, I marked these species as candidates for future pharmacological analysis. At the end of both field seasons, I carefully gathered plant material from these species, being mindful to employ sustainable harvesting methods, to ensure that my methods did not harm the plant populations. At our field station, I established a make-shift herbarium, laying the plant material out to dry on newspapers in a shaded room out of direct sunlight. Maintaining the material's chemical integrity was vital, so each day I visited my herbarium every few hours to turn the samples over and prevent the development of mold. When the plant material was sufficiently dry, I packed everything up into paper bags and shipped my samples to my colleague Fabien Schultz at Neubrandenburg University of Applied Sciences in Germany.

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Pharmacological Testing

In January 2022, I travelled to Neubrandenburg University of Applied Sciences for a month-long visit with my collaborator Dr. Fabien Schultz to begin a crucial phase of my research. This involved conducting extensive pharmacological testing on plant samples that I had exported. Upon arrival, we initiated a series of chemical extractions on these samples which used solvents with different polarities to isolate different compounds from the material. Our focus was twofold: first we assessed each sample's antibacterial properties, testing each species against 11 different dangerous bacterium, then we evaluated each sample's anti-inflammatory properties. Testing spanned several months, leading to the discovery of some remarkable results that promise to contribute significantly to our understanding of these plant resources and their pharmacological potential.

Ethnobotanical Interviews

Lastly, my research explored the potential use of these plants by the local human populations. To investigate, I ventured into the nearby villages to engage in a series of ethnobotanical interviews with local healers. With the invaluable assistance of a translator, I inquired about the specific species I suspected were consumed by chimpanzees and might serve as self-medicative resources. These interviews yielded a wealth of insights, not only shedding light on the local medicinal traditions but also highlighting the conservation status of numerous trees in the region. Many of the healers expressed deep concerns regarding the receding forest cover and its implications for access to these vital healthcare resources. For numerous villagers, who cannot afford trips to the hospital, the local healers and the forest's medicinal plants are their first line of defense against illness. It became evident that there was a significant overlap between the medicinal repertoires of the local populations and some of the resources consumed by the Budongo chimpanzees, emphasizing the intricate connection between humans and the natural environment in this context.

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Explore the Forest (INTERACTIVE)

The feeling of being in the forest, surrounded by tree buttresses and the calls of wild chimpanzees, is difficult to convey through words alone. When I began to notice traces of bark consumption by the chimpanzees I was observing, I wanted to find a way to share my findings with others in an interactive and engaging way - to really convey what these marks look like. To do this, I used 3D scanning to create detailed digital models of some of the trees I was studying. These digital scans not only served as a way of illustrating my research in talks and at conferences , but also as a valuable tool for measuring and analyzing the trees' features once back home in Oxford. 

Tap on a tree to explore the 3D scan - but be patient - it's a little slow to load :)

Conservation Implications

The identification of self-medication behaviors in chimpanzees has significant implications for primate conservation. Protecting primate habitats from rapidly increasing agricultural and commercial activities takes on added urgency when we recognize that the trees in these environments may serve as repositories of remedies vital to the well-being of our primate relatives. With the increasing incidence of virulent anthropogenic pathogens spreading from humans to chimpanzees, there is new urgency for protecting these resources, as the loss of natural remedies may further imperil already vulnerable chimpanzee populations.

 

 

Drug Discovery

 

Conserving medicinal trees may not only help our primate cousins, it will likely also benefit us. By preserving chimpanzee habitats and studying their self-medication practices, we not only protect our primate cousins but also create an invaluable reservoir of knowledge that could hold the answers to future global health crises. The recent global pandemic served as a stark reminder of our urgent need for new medicines to tackle the rapidly growing problem of novel pathogens and drug-resistance. As the growing threat of anthelmintic and antibiotic resistant pathogens looms large, we may need to return to nature’s pharmacies for solutions. At this point, we are not only fighting to save the chimpanzees and their forest homes, we are fighting for our own survival. But without the chimpanzees to point us in the right direction, will we have a chance at finding the medicines we need? Or will we run out of time? 

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Storytelling & Filmmaking

During the summer of 2022, I embarked on an exciting project with the support of a grant from the Explorers Club and Discovery Inc. My aim was to create two short documentary films, with the help of close friend and collaborator Austen Deery, that captured some of my findings from the field.  Our objective was to offer viewers a glimpse into life in the forest highlighting the role that local field staff play in the production of primatological knowledge, as well as convey the urgency of conserving chimpanzee habitats. Our films touch on the forest's rapid disappearance, which threatens the lives of both the apes and the neighboring human communities.

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Sketches from Budongo

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Snapshots from Budongo