American Journal of Primatology 74:423–432 (2012) RESEARCH ARTICLE Newly Discovered Bale Monkey Populations in Forest Fragments in Southern Ethiopia: Evidence of Crop Raiding, Hybridization With Grivets, and Other Conservation Threats ADDISU MEKONNEN 1∗ , AFEWORK BEKELE 1 , PETER J. FASHING 2 , JEAN-MARC LERNOULD 3 , ANAGAW ATICKEM 4 , AND NILS CHR. STENSETH 4 1 Zoological Sciences Program Unit Faculty of Life Sciences, Addis Ababa University, Addis Ababa, Ethiopia 2 Department of Anthropology and Environmental Studies Program, California State University, Fullerton, California 3 Conservation des Esp` eces et des Populations Animales (CEPA), Schlierbach, France 4 Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, Oslo, Norway Until recently, the Bale monkey (Chlorocebus djamdjamensis), an arboreal primate endemic to the southern Ethiopian highlands, remained virtually unstudied, and its distribution pattern inadequately documented. To broaden our knowledge of the species’ distribution and abundance, we carried out in- terviews with local people and total count surveys for Bale monkeys across 67 fragmented forest sites in human-dominated landscapes in the Oromia and Southern Nations, Nationalities, and People’s Regions, Ethiopia. From January 2010 to May 2011, we discovered 26 new Bale monkey populations inhabiting forest fragments at elevations ranging from 2,355 to 3,204 m asl. Across these populations, we recorded 37 groups ranging in size from 9 to 29 individuals (Mean = 19.5, SD = 4.5), for a total of 722 individuals. Black-and-white colobus monkeys (Colobus guereza) were sympatric with Bale monkeys at all sites, while grivet monkeys (Chlorocebus aethiops) were found only at sites where Bale monkeys did not occur. All of the newly discovered Bale monkey sites once contained bamboo forest, though at 35% of the sites bamboo forest had been eliminated during the past two decades. The persistence of Bale monkeys at fragmented sites lacking bamboo suggests greater habitat flexibility for the species than previously thought, though the long-term viability of populations both with and without bamboo remains uncertain. Human hunting in response to crop raiding, a behavior the monkeys engaged in at all sites, represents a major threat facing the newly discovered Bale monkey populations. Further- more, despite their current lack of sympatry, apparently hybrid individuals between Bale monkeys and grivets were noted at three sites, posing yet another potential obstacle to Bale monkey conser- vation. Community conservation programs aimed at (1) protecting remaining habitat fragments, (2) planting bamboo and trees within and between fragments, and (3) reducing crop raiding represent the only hope for survival of the newly discovered Bale monkey populations. Am. J. Primatol. 74:423–432, 2012. C  2012 Wiley Periodicals, Inc. Key words: Chlorocebus djamdjamensis; conservation; crop raiding; distribution; forest fragmen- tation; hybridization INTRODUCTION Nonhuman primates face a variety of an- thropogenic threats including habitat destruction, hunting, infectious disease, and climate change [Chapman et al., 2006; IUCN, 2010]. The most se- rious immediate threat to the survival of many primate species is habitat destruction for timber, agricultural land, and human settlement [Isabirye- Basuta & Lwanga, 2008; IUCN, 2010]. Habitat loss has forced many primate populations to live in small fragments isolated from one another by human- dominated landscapes [Marsh, 2003]. Conversion of primate habitats into agricul- tural land, in particular, creates the potential for conflict between hungry primates and peo- ple [Campbell-Smith et al., 2010; Cowlishaw and ∗ Correspondence to: Addisu Mekonnen, Zoological Sciences Pro- gram Unit, Faculty of Life Sciences, Addis Ababa University, PO Box 1176, Addis Ababa, Ethiopia. E-mail: addisumk@yahoo.com Contract grant sponsor: Conservation des Esp` eces et des Pop- ulations Animals (CEPA); contract grant sponsor: Zoologis- che Gesellschaft f ¨ ur Arten- und Populationsschutz, Germany (ZGAP); contract grant sponsor: Le Conservatoire pour la Protec- tion des Primates; contract grant sponsor: La Vall´ ee des Singes Primate Park. Received 25 August 2011; revised 17 November 2011; revision accepted 19 November 2011 DOI 10.1002/ajp.21999 Published online 6 February 2012 in Wiley Online Library (wileyonlinelibrary.com). C  2012 Wiley Periodicals, Inc.