International Journal of Primatology | 2021
Feeding Ecology of the Omo River Guereza (Colobus guereza guereza) in Habitats with Varying Levels of Fragmentation and Disturbance in the Southern Ethiopian Highlands
Abstract
Dietary responses to the habitat heterogeneity resulting from anthropogenic disturbance vary among primates. Some species alter their foraging strategy and continue to thrive in human-modified habitats while others are unable to modify their diets sufficiently to cope with such disturbance. Over a 12-mo period, we investigated the feeding ecology of the Omo River guereza (Colobus guereza guereza), a subspecies of black-and-white colobus monkeys endemic to Ethiopia, in a large continuous forest (Munessa: LC group), a smaller modified continuous forest (Wondo Genet: SC group), and a tiny forest fragment (Aregash: F group). We found that the forest fragment had higher tree stem densities but lower overall tree basal area than the continuous forests. In all three forests, guerezas were mostly folivorous (LC group: 83%; SC group: 65%; F group: 62%) and consumed young leaves in accordance with their availability. However, in addition to these broad dietary similarities, there were several differences between forests suggesting strategies guerezas may use to cope with habitat heterogeneity in southern Ethiopia. We found that guerezas in anthropogenically altered forests relied less on mature leaves and more on whole fruits (F group) or flowers (SC group) than guerezas in large continuous forest (LC group). Guerezas also devoted large percentages of their feeding time to exotic species in disturbed forests (SC group: 49.0%; F group: 20.6%) but not in the large continuous forest (LC group: 0.0%). Lastly, guerezas in disturbed forests had richer diets (F group, N = 37 species, SC group, N = 32) than those in the large continuous forest (LC group, N = 27). Thus, our study found that within the folivorous dietary strategy of guerezas, there is considerable dietary variability among even neighboring populations experiencing different degrees of habitat fragmentation and degradation. This dietary flexibility may explain the relatively high tolerance of guerezas to human disturbance across their geographic distribution.