MSc research in the Volcanoes National Park, Rwanda: Sept-Oct 2015

I have conducted one month fieldwork in the Volcanoes National Park (VNP), for the study on the ''abundances and distribution of the five most preferred food species for the mountain gorillas''. The VNP is one of the 3 parks forming the Virunga Massif, a mountainous landscape with elevation range up to 4,507 m a.b.s.l. The Virunga area is shared between Rwanda, Uganda and the Democratic Republic of Congo (DRC).

The data collection focused on recording the species locations and the characteristics of their habitat: canopy closure, tree density, tree height and diameter at the breast height. These parameters constitute environmental variables which determine the species occurrences. The species to be mapped were below canopy, so direct mapping was not possible. Indirect mapping; to link species locations and ecological conditions is also a used technique to find where species occur in a targeted ecosystem. More variables were extracted using Geographic Information System: from the Digital Elevation Model (DEM), a number of topographic variables could be extracted. Using a certain model, species distribution maps are produced, and they show the probability of occurrence of concerned species. For my study I used the Boosted Regression Tree model (BRTs), that uses absence and presence along with extracted environmental factors, to produce the probability of occurrences of species and the most important predictor variable.

Mountain gorillas (Gorilla beringei beringei) are herbivorous and they mostly consume leaves, stems, barks, fruits or roots of plants. In the VNP, around 54 plant species compose the food for the gorilla, but five species form approximately 80% of their diet; which means that the gorilla spends much time feeding on these particular species. These species were mapped, to contribute to the continuous monitoring of food species for these endangered primates, with a an increasing population. It is very important to understand the dynamics of vegetation with regard to an increasing herbivore population in the park.

The mapping also is a crucial step in determining the movements of animals, with a changing climate. The current suitable habitat for the gorilla is in the mid-altitude of the VNP which correspond to the abundances of the food for the gorilla. However, some consumed plants are likely to occur in the higher elevations, hence making some gorilla groups spending time in the sub-alpine zones of these mountains. Repeated mapping of these plants could indicate whether there are altitudinal shifts in some vegetation, and hence changes in the gorilla suitable habitat.

This research has boosted my study design, sampling and modelling skills. The fieldwork was much interesting with the assistance of field guides from the Rwanda Development Board - VNP team. I also had a chance to present my research at the Karisoke Research Centre in Musanze, an office for the Dian Fossey Gorilla Fund International in Rwanda. It was an opportunity to meet Martha Robbins from the Max Planck Institute for Evolutionary Anthropology, Germany. Martha has been involved in mountain gorilla research for some years, and she was nice to me, at the point to allow sharing of an existing dataset on gorilla food species from her research team. I still keep in mind such a great support from her ;). Basically with statistics, you need enough records (samples) so to have good results from your model.

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