An arboreal and folivorous monkey, the endangered ashy red colobus (Piliocolobus tephrosceles) exists across dry deciduous savanna woodland in Tanzania

Assessment of population status and threats for primates is critical to their conservation because it helps in identifying areas of high protection value for effective management planning. The ‘Endangered’ ashy red colobus monkey ( Piliocolobus tephrosceles) occurs in the western parts of Uganda and Tanzania. Here we present the first extensive survey of ashy red colobus in the Greater Mahale Ecosystem (GME), a vast landscape dominated by dry deciduous savanna woodland habitat. We walked a total distance of 995 km from July 2015 to August 2017, encountering a total of 160 groups in the ecosystem. Group encounters were higher in forest (0.3 groups/km) than woodland (0.01 groups/km) vegetation types. Estimated group and individual densities were higher in forest (4.2 groups/km 2 ; 142.9 individuals/km 2 ) than woodland (0.11 groups/km 2 ; 5.8 individuals/km 2 ) vegetation types. We report for the first time the presence of the species in the most northern and eastern part of the GME. A variety of anthropogenic activities were observed in the GME, beekeeping and pit sawing being the most frequent. Our finding that an arboreal primate, described as mainly folivorous, can exist in large numbers in such open and dry savanna woodland habitat with very little evergreen vegetation provides further evidence of the species’ ecological flexibility and challenges the assumption that this habitat type is less important than wet, evergreen forest for the conservation of ashy red colobus monkeys.