Chimpanzee seed dispersal in Rwanda

Nicole Gross-Camp, PhD student

The Nyungwe Forest National park, Rwanda, Central Africa

Nico, Nico! Venez ici!

I moved toward the large Parinari tree where my field assistant, Abraham, stood. As I made my way through the dense understory, the woody remnants of Mimulopsis tugged at the loopholes on my shoelaces. The pungent scent of its flowers brushed my hair. Blooming only every seven to ten years, I delighted in this opportunity. I tried to imagine the pollen transformed into a flavorful honey coveted by Rwandans. As I approached where Abraham was standing a broad smile crept across his face. The flash of his white teeth in contrast to his dark skin was electrifying.

Nico, voila nos richesses!

Abraham’s hand swept over a pile of freshly deposited chimpanzee dung full of beautiful Olea capensis seeds.

I recently returned from a six month field season in the Nyungwe Forest Reserve, Rwanda, where I began my graduate research. The Nyungwe Forest is a large reserve, 950 km2, located in southwestern Rwanda. The Reserve connects with the Kibira National Forest, Burundi, forming one of the largest remaining montane forests in Africa. The Nyungwe Forest is part of the Albertine Rift, the western branch of the Great Rift Valley, and contains an extraordinary diversity of flora and fauna including numerous endemic species. Its undulating landscape is quite literally breathtaking and indicative of Rwanda’s name, Milles Collines, thousand hills. Unlike the hot savannah, the mountainous landscape offers a cool and temperate climate and is home to 13 species of primate, including the elusive owl-faced guenon (Cercopithecus hamlyni) and black and white colobus (Colobus angloensis ruwenzorii), the latter of which live in huge ‘supergroups’ of 300+ individuals.

I went to the Nyungwe Forest to commence my own graduate research on the seed dispersal behavior of the chimpanzee (Pan troglodytes schweinfurthii). The chimpanzee is the largest remaining frugivore, or fruit-eating, mammal remaining in the forest. The chimpanzee has a large home-range, may move up to several kilometers a day, and a voracious appetite for fruit. Prior research involving the chimpanzee indicates the species tendency to swallow seeds whole, passing them unharmed in their feces. In addition, the chimpanzee has been documented to enter degraded or disturbed areas and may contribute to regeneration processes by depositing seeds in these areas.

My research involves an examination of the fate of large fruit seeds (> 5 mm) deposited by a chimpanzee: once deposited, are the seeds destroyed by predators or pathogens? Do they experience secondary dispersal by another animal or insect? Or, do they reach germination and successfully establish as seedlings? Answering these questions may help us to understand the ecological role of chimpanzees in important forest processes such as regeneration. Similarly, my research may give insight into chimpanzees’ role in structuring plant communities and maintaining biological diversity.

The gift of good field assistants is priceless. Abraham had the drive, skill, and knowledge of the forest to be an excellent assistant, but equally important he possessed a great sense of humor. We found seven chimpanzee fecal samples my first day in the field followed by two days of the chimpanzees eluding us. Abraham’s advice was this:

N’inquiétez pas, Nico. Ils sont nos richesses, nous irons les trouver.
(Don’t worry, Nicole. They are our riches, we will find them.)

Additional information may be found at:

  • The Albertine Rift Conservation Society
  • Plumptre, A.J., Masozera, M., Fashing, P.J., McNeilage, A., Ewango, C., Kaplin, BA, Liengola, I. Biodiversity Surveys of the Nyungwe Forest Reserve in S.W. Rwanda. WCS Working Papers No. 18, May 2002. Available for download from http://www.wcs.org/science/