Microhabitat Use in Angolan Colobus Monkeys (Colobus angolensis ruwenzorii) at Nabugabo, Uganda Demonstrates Intraspecific Variability

Abstract

Large-scale anthropogenic changes to the environment are making it vital to investigate habitat use so that we can better understand species’ basic ecological needs in order to create successful conservation plans. Some species are very flexible in their habitat requirements. One such species may be Colobus angolensis ruwenzorii, monkeys that occupy montane and tropical lowland forest. In the mountains of southwestern Rwanda, this species spends a great deal of time on the ground and feeds mainly on mature leaves and lichens, but the habitat use of lower altitude populations is unknown. We examined the fine-scale habitat use of C. a. ruwenzorii at Nabugabo, Uganda (1136 m altitude), where they feed primarily on young leaves and fruits. We used data collected over 9 mo (94 days between July 2017 and April 2018) on 117–131 colobus in 12 core units in a multilevel society. We found that colobus individuals were rarely on the ground, and resting and social behavior occurred at higher heights and in larger trees than feeding and moving. Individual height in the canopy followed a daily pattern (higher at the start and end, with a decrease in the middle of the day) and colobus were at lower heights when group size was greater because of core unit fusion. Finally, we found that tree species were generally used relative to their availability in the forest and their value as food species. Given greater predation risk in smaller groups and lower in the canopy at this site, our results suggest that perceived risk has an important effect on microhabitat use in C. a. ruwenzorii at lower altitude. Our results demonstrate the ecological flexibility of this primate species, which bodes well for their continued conservation.