Chimpanzee Self-Medicative Anecdote Database survey

Chimpanzee Self-Medicative Anecdote Database (CSMAD)



What is the CSMAD?

The Chimpanzee Self-Medicative Anecdote Database (CSMAD) will be an open-access database containing a collection of unusual feeding and self-medicative anecdotes from across chimpanzee field sites. To collect anecdotes for the database we have created the CSMAD survey (accessible below) which will be live from December 25th, 2021 until September 25th, 2022. The aim of this project is to inspire collaborative self-medication studies between field sites, identify possible resources or species of interest, and inspire novel research questions.

As self-medication events and unusual feeding events are rare amongst chimpanzees, sample sizes at any given site are small. This makes it difficult to run statistical analyses on putative or even confirmed self-medication behaviors, making progress in this field difficult and perhaps discouraging for researchers wanting to pursue new insights and novel projects. Collaboration in this topic, especially across field sites, is crucial for the advancement of our understanding of the full scope of animal self-medication.

The survey can be accessed here:

This project is being led by Elodie Freymann as part of her DPhil at the University of Oxford under the supervision of Susana Carvalho, Michael Huffman, and Catherine Hobaiter.


What is chimpanzee self-medication?

Humans have long looked to the behavior of animals as a source of medicinal behavior (Huffman & Seifu, 1989; Huffman, 2001), but it didn’t gain scientific relevance until the late 1970’s. The primatologist, Richard Wrangham’s (1975) PhD on chimpanzee feeding ecology provided the first scientific mention of leaf swallowing behavior, noting the presence of folded, whole leaves in the feces of chimpanzees at Gombe. Independently, the same behavior was also observed in chimpanzees at Mahale by Toshisada Nishida and colleagues, 70 km further south on Lake Tanganyika (Wrangham & Nishida 1983; Huffman, 2015). Daniel Janzen (1978) a feeding ecologist working in Costa Rica, proposed that vertebrate herbivores could be obtaining medicinal benefits from certain plant species. Shortly after this, the study of animal self-medication was given a name, ‘zoopharmacognosy’ (Rodriguez & Wrangham, 1992, 1993).

As of 2016, self-medicative behaviors had been observed in African and Asian great apes across sixteen field sites (Huffman, 2016). Evidence of gorilla self-medication predominantly comes from Kahuzi-Biega (DRC) (Yamagiwa et al., 2005). Evidence of white-handed gibbon self-medication has come from Khao Yai National Park (Thailand) (Barelli & Huffman, 2016). Evidence of orangutan self-medication (specifically fur-rubbing) has come from Central Kalimantan (Borneo) (Morrogh-Bernard, 2008; Morrogh-Bernard et al., 2017). As the most recent list of sites with observed cases of primate self-medication has not been updated since Huffman’s 2016 review, there are likely many unpublished and unrecognized cases.

Non-human self-medication takes many forms and involves a variety of medicinal resources. While bioactive and limitedly nutritious botanical species remain the best studied medicinal resources, clay, and termite-soil (Pebsworth et al., 2012; Krishnamani & Mahaney, 2000), cambium beneath tree bark (Lapuente et al., 2020; Huffman, 1997), and insects (Zito et al., 2003) are also acknowledged as possibly possessing medicinal properties. In recent literature, many other resource types have also been proposed as candidates for further study. However, meeting criteria for intentional self-medication using these resources has been difficult, as medicinal events are rare, and health states must be measured before and after the event.


Types of self-medication

Two known general categories of botanical primate self-medication have been documented in the literature: physical and bioactive. Physical properties of a plant are those which induce a physiological response (e.g., reduction of gut transit time) as a form of self-medication. This involves the ingestion of plant material, which through mechanical properties alone, can alleviate pathogens or parasites via physical expulsion. Leaf swallowing is the commonly cited example of this. Bioactive self-medication involves the ingestion of plant phytochemicals with pharmacological properties. The only conclusive botanical, bioactive, self-medicative behavior thus far is bitter-pith chewing. The only species this has been demonstrated in careful detail thus far is Vernonia amygdalina (Huffman & Seifu, 1989; Huffman et al., 1993).


Self-medication criteria

In 1997, Michael Huffman published a review of the current evidence for self-medication in primates, outlining guidelines to conclusively determine intentional self-medicative behaviors. These criteria include:

  • Infrequent intake of irregularly consumed plant species which provide no/minimal nutritional benefit (Wrangham & Nishida, 1983; Huffman & Seifu, 1989)
  • Restriction of plant use to seasons associated with high parasitic infections (Huffman et al., 1997; Kawabata & Nishida, 1991; Wrangham, 1995)
  • Presence of pathogenic or parasitic infection in the medicator at the time of self-medicative behavior (Huffman & Seifu, 1989; Huffman et al., 1997; Wrangham, 1995)
  • Subsequent improvement in this condition following ingestion (Huffman & Seifu, 1989; Huffman et al., 1993, 1996b)
  • Ingested resource(s) used for medicine in local human communities.


What kind of information are we looking for?

We are looking for interesting anecdotes or examples of possible self-medicative events at your field site or from your own research. These should ideally meet at least two of Huffman’s (1997) intentional self-medication criteria for consideration of inclusion. 

Here are some examples of cases that would be relevant:

1.) Cases in which a chimpanzee who is exhibiting any sickness behaviors has left the group or travelled with perceived intention to a specific, unusual, or apparently non-nutritious resource, which is subsequently consumed.

2.) Cases where a chimpanzee who is exhibiting any sickness behaviors has eaten an unusual or apparently non-nutritious resource and subsequently improved.

3.) Cases where one or multiple chimpanzees exhibits an unusual behavior which involves the ingestion of an unusual food in the presence of symptoms or a specific illness.

4.) Cases where a chimpanzee who may or may not be exhibiting sickness behaviors (i.e. expelling visible worms) leaves the group alone or with a smaller group and leads the way to an unusual or apparently non-nutritious resource.

5.) Cases where a chimpanzee ingests an unusual resource with known ethnomedicinal or medicinal properties.

These events DO NOT have to meet all of Huffman’s (1997) criteria to be applicable but should meet at least two of them. The value of listing of such behaviors is to see how common such events may be across populations and to generate future more detailed investigations of these behaviors and the potential medicinal value of the items ingested.


Why an open access database?

Self-medication events are exceedingly rare. Discovering new intentional self-medicative events requires that the event meet the above listed criteria—which often is impossible due to variables beyond the researcher’s control (i.e. lack of confirmed health improvement following an event). There are likely many putative self-medicative unusual feeding events not recorded in the literature. On their own, these anecdotes are outliers, possibly appearing too inconclusive to publish an account of the event in isolation. However, when anecdotal events are compiled from across the many chimpanzee field sites and sanctuaries, patterns, behaviors, or novel research questions may arise.

Science moves faster when it is collaborative. We believe that data should be open and shared. As this data is mostly descriptive and anecdotal, we believe it will benefit the field of primatology if data can be accessed by all interested parties, and hopefully inspire further research. These results will remain open-access and free for the scientific community to use and analyze.


What do I need to contribute?

Descriptive and anecdotal information about putative self-medication events at your site, along with some contextual information for background and further analysis. If you indicate below that a video was taken of this event, we may follow up with you after the survey has been closed. However, submitting an anecdote does NOT require you to share any videos you have taken.


What will I get from contributing?

If you contribute an anecdote in the first round of this survey you will be given co-authorship on the first submission of the open-access database that will be stored and regularly updated on Zenodo as well as on the first paper published by our team introducing the database and synthesizing results. After September 2022, when the first round of contributions is complete, all contributors to the database will receive a draft of the introductory paper for review.

After the introductory paper is published, the anecdotal data will be transferred to Zenodo and made open-access, so anyone will be able to use and analyze this data. The database will be updated periodically, and anecdote entries will be downloadable for further use.


What if my record is incomplete?

We are happy to have any information, whether or not it is complete. All information in this field is valuable and could create new insight into chimpanzee self-medicative behaviors.


How will the data be used?

The Self-Medication Anecdote Database will include your name and affiliation linked to your observation, unless you choose to be kept anonymous. Your email address will not be published in the database unless you specify that you would like it to, in which case you should provide a professional email. The database will be hosted through Zenodo.

If you have any photographs or videos to complement and support your case that you would be willing to share, please email these to me (, and include a media credit.


What is the timeline?

The questionnaire will be live as of the 25th of December 2021 and responses will be due by September 25th 2022.

An introductory paper synthesizing initial results and introducing the database will be published in February 2023, with more detailed analysis being published in September 2023.


What if the anecdote is previously published?

Please still submit your anecdote. We will do the work of cross-referencing, but please do let us know whether you have published your anecdote in some form.



How to fill out the questionnaire:


How can data be provided?

Data can be provided by filling out the survey (link provided at top of page).


What information will be requested?

Four categories of information will be requested: field site details, complementary information about the event, specific information about the anecdote, and optional contact details for follow up questions about the anecdote and co-authorship.

Below is a list of minimal requirements for an anecdote submission:

  • Chimpanzee sub-species (Field site details)
  • Field site name (Field site details)
  • Community name (Field site details)
  • Date of anecdote (Field site details)
  • Is this personal data or long-term data from the field site? (Field site details)
  • Population Type (Field site details)
  • Resource Type (Event specific)
  • Processing Type (Event specific)
  • Was the individual’s health status known during this event (ie. parasite load, presence of sickness behaviors? (Event specific)
  • Event habitat (Event specific)
  • Season (Event specific)
  • Was rainfall data recorded at this site during the period this event was recorded (Event specific)
  • Was this event filmed? (Event specific)
  • Observer Name (Contact info)
  • Affiliated Institution of Observer (Contact info)
  • Email of submitter (Contact info)
  • Would you like to be listed as anonymous? (Contact info)
  • Would you mind being contacted for follow up questions? (Contact info)


Entering information

Please fill out the survey using the drop-down menus. When there in a question which requires further free written answers, a box will appear below the multiple-choice question. If the question is not applicable, or no answer is known, please skip the question.


English as a second language

The online survey form is written in English. If you would like to share this survey with an individual who is more comfortable in a language not listed above, please get in touch and we will do our best to provide further translations to make the Self-Medicative Database more inclusive and accessible.


This project is being led by Elodie Freymann as part of her DPhil at the University of Oxford under the supervision of Susana Carvalho, Michael Huffman, and Catherine Hobaiter. This project was inspired by the Thanatobase led by Dr. Alecia Carter.



Barelli, C., & Huffman, M. A. (2016). Leaf swallowing and parasite expulsion in Khao Yai white-handed gibbons (Hylobates lar), the first report in an Asian ape species. American Journal of Primatology, 79(3), 1–7.

Huffman, MA., Seifu, M. (1989). Observations on the illness and consumption of a possibly medicinal plant Vernonia amygdalina (Del.), by a wild chimpanzee in the Mahale Mountains National Park, Tanzania. Primates, 30(1), 51–63.

Huffman, M. A., Gotoh, S., Izutsu, D., Koshimizu, K. & Kalunde, M. S. (1993). Further observations on the use of the medicinal plant, Vernonia amygdalina (Del) by a wild chimpanzee, its possible effect on parasite load, and its phytochemistry. African Study Monographs 14(4): 227-240.

Huffman, MA., Page, JE., Sukhdeo, MVK., et al. (1996b). Leaf‐swallowing by chimpanzees: a behavioral adaptation for the control of strongyle nematode infections. International Journal of Primatology 17:475–503.

Huffman, M. A., & Caton, J. M. (2001). Self-induced increase of gut motility and the control of parasitic infections in wild chimpanzees. International Journal of Primatology,  22(3), 329–346.          

Huffman, MA. (1997). Current evidence for self-medication in primates: a multidisciplinary perspective. American Journal of Physical Anthropology, 104(S25), 171–200.

Huffman, MA. (2015). Chimpanzee self-medication: A historical perspective of the key findings. In M. Nakamura, K. Hosaka, N. Itoh, & K. Zamma (Eds.), Mahale Chimpanzees: 50 Years of Research (pp. 340-353). Cambridge: Cambridge University Press.

Huffman, MA. (2016). Primate self-medication, passive prevention and active treatment—A brief review. International Journal of Molecular Sciences, 3, 1–10.

Janzen, D. H. (1978). Complications in interpreting the chemical defenses of trees against tropical arboreal plant-eating vertebrates. In The Ecology of Arboreal Folivores, ed. G. G. Montgomery. Washington DC: Smithsonian Institute Press, pp. 73–84.

Kawabata, M., Nishida, T. (1991). A Preliminary Note on the Intestinal Parasites of Wild    Chimpanzees in the Mahale Mountains, Tanzania. Primates 32, 275–278.

Krishnamani, R., & Mahaney, W. C. (2000). Geophagy among primates: Adaptive significance and ecological consequences. Animal Behaviour, 59(5), 899–915.

Lapuente, J., Arandjelovic, M., Kühl, H. et al. (2020). Sustainable Peeling of Kapok Tree (Ceiba pentandra) Bark by the Chimpanzees (Pan troglodytes verus) of Comoé National Park, Ivory Coast. International Journal of Primatology, 41, 962–988.

Morrogh-bernard, H. C. (2008). Fur-Rubbing as a Form of Self-Medication in Pongo pygmaeus. 1059–1064.

Morrogh-Bernard, H. C., Foitová, I., Yeen, Z., Wilkin, P., De Martin, R., Rárová, L., … Olšanský, M. (2017). Self-medication by orang-utans (Pongo pygmaeus) using bioactive properties of Dracaena cantleyi. Scientific Reports, 7(1), 1–7.

Rodriguez, E. and R.W. Wrangham. (1992). Zoopharmacognosy: Medicinal plant use by wild apes and monkeys. Paper presented at the meetings of the American Association for the Advacenment of Science (AAAS). Chicago.

Rodriguez, E., Wrangham, RW. (1993). Zoopharmacognosy: The use of medicinal plants by animals. In K.R. Downum, J.T. Romeo and H.A. Stafford, eds., Recent Advances in Phytochemistry. Vol. 27, pp. 89-106. New York: Plenum Press.

Roode, J. C. De, Lefèvre, T., & Hunter, M. D. (2013). Self-Medication in Animals. 340(April), 150–152.

Wrangham, RW. (1975). The behavioural ecology of chimpanzees in Gombe National Park [PhD Thesis]. Cambridge, UK: University of Cambridge.

Wrangham, R. W., Nishida, T. (1983). Aspilia spp. Leaves: A puzzle in the feeding behavior of wild chimpanzees. Primates, 24(2), 276–282.

Wrangham RW. (1995). Relationship of chimpanzee leaf‐swallowing to a tapeworm infection. American Journal of Primatology 37:297–303.

Yamagiwa, J., Basabose, A. K., Kaleme, K., & Yumoto, T. (2005). Diet of Grauer’s gorillas in the Montane Forest of Kahuzi, Democratic Republic of Congo. International Journal of Primatology, 26(6), 1345– 1373.

Zito, M., Evans, S., Weldon, PJ. (2003). Owl monkeys (Aotus spp.) self-anoint with plants and millipedes. Folia Primatologica 74: 159–161.


Other key readings:

Clayton, DH., Wolfe, ND. (1993). The adaptive significance of self-medication. Trends in Ecology & Evolution 8: 60–63.

Huffman, MA., Hirata, S. (2004). An experimental study of leaf swallowing in captive chimpanzees: insights into the origin of a self-medicative behavior and the role of social learning. Primates, 45(2), 113–118.

Huffman, MA., Spiezio, C., Sgaravatti, A., Leca, J. B. (2010). Leaf swallowing behavior in chimpanzees (Pan troglodytes): biased learning and the emergence of group level cultural differences. Animal Cognition, 13(6), 871–880.

Villalba, JJ, Provenza, FD., Shaw, R. (2006). Sheep self-medicate when challenged with illness-Inducing foods. Animal Behaviour, 71, 1131–1139.