Energetic responses to variation in food availability in the two mountain gorilla populations (Gorilla beringei...

Here, we compare food availability and relate this to differences in energy intake rates, time spent feeding, and daily travel distance of gorillas in the two populations. Comparative intraspecific studies investigating spatiotemporal variation in food availability can help us understand the complex relationships between ecology, behavior, and life history in primates and are relevant to understanding hominin evolution. Differences in several variables have been documented between the two mountain gorilla populations in the Virunga Massif and Bwindi Impenetrable National Park, but few direct comparisons that link ecological conditions to feeding behavior have been made.

Using similar data collection protocols we conducted vegetation sampling and nutritional analysis on important foods to estimate food availability. Detailed observations of feeding behavior were used to compute energy intake rates and daily travel distance was estimated through GPS readings.

Food availability was overall lower and had greater temporal variability in Bwindi than in the Virungas. Energy intake rates and time spent feeding were similar in both populations, but energy intake rates were significantly higher in Bwindi during the period of high fruit consumption. Daily travel distances were significantly shorter in the Virungas.

Overall, despite the differences in food availability, we did not find large differences in the energetics of gorillas in the two populations, although further work is needed to more precisely quantify energy expenditure and energy balance. These results emphasize that even species with high food availability can exhibit behavioral and energetic responses to variable ecological conditions, which are likely to affect growth, reproduction, and survival.