Diet variability of mountain gorillas in Bwindi Impenetrable National Park, Uganda

Ganas, Jessica
Beth Kaplin, PhD
Department of Environmental Studies
Examining intraspecific dietary variability has important implications of understanding flexibility in foraging behavior, habitat utilization, population dynamics, and social behavior and may also assist in conservation efforts. We compared food availability and diet of one group of mountain gorillas (Gorilla beringei beringei) at a high altitude site and two groups at a low altitude site within Bwindi Impenetrable National Park, Uganda from September 2001 to August 2002. Plant species diversity was greater at the low altitude site than the high altitude site. The two groups at the low elevation consumed more plant species (140 species vs. 62 species), and a greater number of fruit species per month (7 vs. 3 species) and per year (36 vs. 11 species) than the high altitude group. Furthermore, each group shared less than 51% of important fibrous food items in their diet with the other two groups. We found no significant differences in the proportion of days fruit remains were found in the dung between groups. Finally, according to Ivlev's electivity index, all groups positively selected the majority of food items in their diets. We attribute a large proportion of dietary variation between locations to differences in fruit availability and plant species composition between sites. We suggest that differences between groups at the lowland site may be due to group traditions, or variation in food profitability (more profitable foods available to choose in the same area) within their overlapping home range, but more research is needed to test these hypotheses. A comparison of our results with the diet of gorillas of the Virunga Volcanoes in Rwanda and Kahuzi-Biega, DRC shows that eastern gorilla populations have highly variable dietary patterns with limited overlap in species consumed between groups and populations.

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