Reliable data on the distribution and threats facing primate species are crucial to identifying priority sites for conservation and designing effective management plans. Boutourlini's blue monkey (Cercopithecus mitis boutourlinii) is a little-known arboreal primate endemic to the forests of western Ethiopia. This subspecies is categorized as Vulnerable on the International Union for Conservation of Nature (IUCN) Red List and the distribution of extant populations is largely unknown. To increase our knowledge of the spatial distribution and conservation status of Boutourlini's blue monkey, we carried out intensive reconnaissance surveys from January 2010 to May 2011 across approximately 40% of its potential range and conducted interviews with local people at each of the survey locations. We carried out geospatial analyses and mapped the distribution of Boutourlini's blue monkey localities with respect to elevation, protected area status, and changes in forest cover over time using ArcGIS 10.4.0. Through our surveys, we discovered 30 previously unknown Boutourlini's blue monkey populations in three administrative regions of western Ethiopia (Amhara, Oromia, and Southern Nations, Nationalities and People's Regions). A total of 34 different groups were sighted and counted at the survey sites, averaging 14.7 members (range 8-23) per group. There are now 32 Boutourlini's blue monkey populations of recently confirmed occurrence at altitudes ranging from 1039 to 2780 m asl, seven in forests of greater than 50 km2. Crop feeding by Boutourlini's blue monkeys was reported by people at seven sites and confirmed through direct observation at three of these sites. None of the known extant populations of Boutourlini's blue monkeys occur within a strictly protected area (e.g., national park) where exploitative human activities are outlawed. A complete reassessment of the distribution and conservation status of Boutourlini's blue monkey will require further surveys across the remaining approximately 60% of its potential range.
Keywords: ArcGIS; Deforestation; Forest fragment; Guenon; Protected area; Tropical montane rainforest.