The Research


Male Bioko Drill 2015. Photo by Tania Escobar

The Bioko Island drill is one of the largest vertebrate species remaining in the forests of Bioko Island and an IUCN endangered species throughout its range. Similar to other primates on Bioko Island, they are mainly threatened by bushmeat hunting and habitat destruction. Surprisingly, despite being characterized as the African primate in greatest need of conservation action, they have rarely been studied in the wild.

As we filmed the Bioko Island drills for our conservation film, we quickly noticed how valuable the footage that we were collecting was for answering wildlife research and management questions. Since all of our filming is done in camouflaged blinds that are strategically placed near feeding trees, we were able to not only film but also record activity budgets for a number of individuals each time they were encountered. These activity budgets have now given us an idea of how much time a drill spends in various activities such as eating, resting and moving when at feeding trees.

These animals are not habituated and great care is taken to ensure our research methods are ethically sound as to not harass the drill monkeys or alter their behavior in any way. Such observation methods are needed to ensure the safety of study animals found within areas of high level of hunting and poaching.

tdp hide

TDP researchers collect data from blinds to conceal observers.

The footage that we collect from the blinds together with a number of strategically placed GoPro cameras and other camera traps have provided us with critical data about the drills in their natural habitat. We now have information about drills presence/absence at feeding trees, abundance, habitat use, foraging patterns, group composition etc…


The results from our studies is used to inform and involve local institutions and stakeholders, including local and national authorities and the international conservation community in protection of Bioko Island’s drills and other wildlife.

Other Drill Researchers

The Drill  Project isn’t the only research project exploring the lives of drills.  Below are some of the world’s top experts on drills and friends of the project. We are still updating this list so check back to see others and learn how they are trying to understand and protect these amazing animals.

jakeownes2Jake Owens Ph.D.

The doctoral dissertation of Dr. Owens represented the first ecological study of the Bioko Island drill monkey (Mandrillus leucophaeus poensis), a highly endangered monkey subspecies endemic to Bioko Island. Owens employed primary and secondary observational techniques, fecal sample analysis, habitat assessments and botanical surveys, and stable isotope analysis to determine the impact of habitat and resource variations on the ecology and behavior of drills. Owens continues his work on Bioko Island drills through his collaboration with The Drill Project, where the goal of his work is to enable us to better aim the conservation efforts taking place throughout the range of drills by identifying key habitats to protect based on empirical data.

Owens received his Ph.D. in Environmental Science from the Department of Biodiversity, Earth, and Environmental Sciences at Drexel University in 2013. He is currently a behavior researcher at the Chengdu Research Base of Giant Panda Breeding, where his focus is on the development and implementation of the giant panda reintroduction program in Sichuan Province, China.


Christos_AstarasChristos Astaras Ph.D.

Dr. Astaras’s doctoral research on the drill monkeys examined for the first time systematically the diet of the species throughout the year and challenged the then dominant assumptions about the drill group structure (widely believed to consist of single adult male family units that only temporarily aggregate in large groups – hordes). Together with Dr. Bethan Morgan of the Ebo Forest Research Project, he conducted a Cameroon-wide survey of the drill status in the country and brought attention at the increasingly fragmented distribution of the species and the importance of the Ebo and Korup populations. Currently, using data from passive acoustic sensors in Korup and Rumpi Hills Rorest Reserve, Asteras is part of a team that tries to develop automatic detection algorithms for the species, which can help improve drill monitoring over large areas in the future.

Asteras received his Ph.D. from the Centre for Nature Conservation of Göttingen University, Germany in 2008. Since then, he has remained involved in conservation research in the broader Korup region and the protection of its rich primate community. Currently he is a postdoctoral researcher at the Wildlife Conservation Research Unit (WildCRU) of University of Oxford where he coordinates a multi-partner Darwin initiative project that examines the efficacy of anti-poaching patrols in Afrotropical protected areas using novel acoustic monitoring methods.

Published Articles on Drills

If you are interested in learning more about drill research read the following articles that are published by some of the experts in the field.

Astaras, C., Krause, S., Mattner, L., Rehse, C., Waltert, C. (2011). Associations between the drill (Mandrillus leucophaeus) and sympatric primate species in Korup National Park, Cameroon. American Journal of Primatology 73:127-134.

Astaras, C., Waltert, M. (2010). What does seed handling by the drill tell us about the ecological services of terrestrial cercopithecines in African forests? Animal Conservation 13:568-578.

Astaras, C., Mühlenberg, M., Waltert, M. (2008). Note on drill (Mandrillus leucophaeus) ecology and conservation status in Korup National Park, Southwest Cameroon. American Journal of Primatology 70:306-310.

Astaras C. (2009). Ecology and Status of the Drill (Mandrillus leucophaeus) in Korup National Park, Southwest Cameroon: Implications for Conservation. Georg-August University of Göttingen. Pp 284.

Eberhard M. L., J. R. Owens, H. S. Bishop, M. E. de Almeida, A. J. da Silva, G.W. Hearn, S. Honarvar. Cyclospora spp. in drills, Bioko Island, Equatorial Guinea. (2014). Emerging Infectious Diseases 20:510–511.

Morgan, B., Abwe, E., Dixson, A., Astaras, C. (2013). The distribution, status and conservation outlook of the drill (Mandrillus leucophaeus) in Cameroon. International Journal of Primatology 34:281–302.

Ting, N., Astaras, C., Hearn, G., Honarvar, S., Corush, J., Burrel, A., Phillips, N., Morgan, B., Gadsby, E., Raaum, R., Roos, C. (2012). Genetic signatures of a demographic collapse in a large-bodied forest dwelling primate (Mandrillus leucophaeus). Ecology and Evolution 2:550-561.

Worobey, M., P. Telfer, S. Souquiere, M. Hunter, C. A. Coleman, M. Makuwa, G. W. Hearn, S. Honarvar, P. Roques, C. Apetrei, M. Kazanji and P. A. Marx. (2010). Island Biogeography Reveals the Deep History of SIV. Science. 329, p. 1487

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