On the move: Activity budget and ranging ecology of endangered Ashy red colobus monkeys (Piliocolobus tephrosceles) in a savanna woodland habitat

Abstract

The majority of primate species are under the threat of extinction and their numbers are decreasing worldwide mainly due to human activities. Most primates outside protected areas survive in habitats with different degrees of anthropogenic alterations. Thus, the persistence of a primate species across its geographic range partly depends on the ability of its populations to adapt to diverse habitats with different spatiotemporal patterns of food availability. Understanding the ecological and behavioral adaptations of a particular species to the different habitats it occupies is crucial for designing a comprehensive conservation approach that can also benefit sympatric wildlife species. Ashy red colobus (Piliocolobus tephrosceles) are arboreal, folivorous and endangered monkeys that occur in Uganda and Tanzania. They have been studied in forest habitats, but very little is known about their behavior and ecology in savanna woodland and how these arboreal and folivorous monkeys can survive in such dry habitats. To better understand this species’ range of adaptations, from July 2016 to June 2018 we conducted a comparative study of habitat quality, activity budget and ranging ecology of two groups of Ashy red colobus monkeys living in distinct habitats in western Tanzania: savanna woodland and forest mosaic. We found that the savanna woodland group spent significantly more time moving and less time feeding than the forest mosaic group. We also found that the savanna woodland group had a larger home range, core areas and mean daily travel distance than the forest mosaic group. The savanna woodland group had the largest home range size ever reported for Ashy red colobus monkeys or other red colobus species. Seasonal differences in home range and core area size were found for the forest mosaic group (both were larger in the dry than in the wet season) but not for the savanna woodland group. The patchy spatial distribution and lower density of most of the preferred food tree species of Ashy red colobus monkeys in the savanna woodland seemed to influence their ranging behavior in this habitat. These results expand our understanding of colobine behavioral and ecological flexibility and provide critical data to formulate workable conservation strategies that encompass the whole range of habitats occupied by Ashy red colobus monkeys. Our study also helps to better understand the ecological constraints that savanna woodland habitats pose on primates.