Ecological and social drivers of range use in the endangered red colobus monkeys (piliocolobus tephrosceles) in Kibale National Park, Uganda

Abstract

To fully understand the behavioral responses and adaptations of leaf-eating primates to the changing environment and interaction with other primates, ranging pattern data are crucial. For this study, I investigated home range use of the red colobus monkey (Piliocolobus tephrosceles) in relation to food availability and the behavior of other primates in Kibale National Park, Uganda. The study used long-term (plant phenology (2006 – 2021) and behavioral (2010 – 2016)) data and new behavioral data (Dec-2022 until May 2023) from a well-habituated group of red colobus monkeys. Long-term phenology data were used to examine the temporal change in food availability and its effect on red colobus home range sizes. Long-term behavioral data were used to estimate seasonal home range sizes using the Autocorrelated Kernel Density Estimation (AKDE). New data were used to assess seasonal movement patterns of the group in response to the location of feeding trees and interactions with other primates. Results indicate that food availability is lower in the dry than the wet season. Home range area was smaller in the dry season and larger in the wet season. However, according to the statistical model, this difference was not clearly significant (p = 0.0518). Further, the statistical models revealed that young leaf availability did not have significant effects on home range size (p = 0.542). According to the new data, the group ate from 182 trees from 36 species in the wet season, and from 80 trees from 19 species in dry season, and Prunus africana was the topmost consumed plant species. In all seasons, red colobus associated more often with the red-tailed monkeys than with other primates. Considering seasonal differences, red colobus traveled longer distances in the wet season, both alone (7,781 m) or in association with other monkeys (7,702 m), compared to the distances travelled during the dry season, alone (3590 m) or in association with other monkeys (3420 m). Therefore, ranging in red colobus appears to be influenced by changes in food, particularly, feeding tree species, but not by polyspecific associations. This implies that, going forward, evaluating the relationships between food tree species and red colobus range use is relevant for identifying habitat patches with keystone tree species to guide restoration and protecting thus strengthening habitat quality for the monkeys