The Bale monkey (Chlorocebus djamdjamensis) is endemic to Ethiopia. Balernmonkeys are recorded as Data Deficient in the IUCN Red List of Threatenedrnspecies categories. This study was conducted from August 2007 to May 2008 torndetermine the habitat preference, population size, feeding ecology, activity andrnranging patterns of the Bale monkey in the Odobullu Forest and distributionrnpattern across the Bale Mountains, Ethiopia. A total of 136 censuses of 1.8 to 3.2rnkm transects were conducted with a cumulative distance of 302.4 km in threerndifferent habitat types. A total of 62 Bale monkey groups were sighted and all ofrnthe encounters were observed in the bamboo forest habitat. In addition, the twornstudy groups spent all group scan time exclusively in the bamboo forest habitatrnirrespective of seasons. Thus, Bale monkeys could be considered as bamboornforest specialists. The average group encounter rate of the monkeys in thernbamboo forest was 0.44 per km and the average density was 124.69 per km2.rnThe total population of Bale monkeys in the Odobullu bamboo forest is estimatedrnto be 1746 individuals. The distribution of Bale monkeys in the Odobullu Forestrnwas interlinked with bamboo forest habitat. The presence or absence of Balernmonkeys in the bamboo forest habitat with altitude between 2400-3250 m aslrnwas surveyed in the Bale Massif and three new Bale monkey populations wererndiscovered. The activity pattern, feeding ecology and ranging behaviour werernstudied in two neighbouring groups with 15 minutes interval scan sampling forrneight month study period. Feeding comprises the majority of their activity timernwith 65.7% followed by moving and resting that comprises 14.4% and 10.7%,rnrespectively. Bale monkeys spent 7.1% of their time for social and the remainingrn2.4% for other activities. The overall diet composition of Bale monkeys wasrndominated by young leaves, contributing 80.2%. In addition, they feed on fruitsrn(9.6%), flowers (3.1%), animal preys (2.3%), shoots (1.5%), stems (1.4%),rnmature leaves (1.1%) and roots (0.9%). Bale monkeys consumed a total of 11rnplant species, of these, the top five accounted 94.3% of their overall diet. Ofrnthese, bamboo (Arundinaria alpina) contributed 76.7% of their overall diet, ofrnwhich 73% was from young leaves. The mean daily range length for the studyrngroups was 928 m and the average yearly home range size of the study groupsrnwas 15.2 ha. The narrow ecological niche of the species may be a threat for itsrnsurvival due to the bamboo harvest by local people for commercial purposes.rnThe population status and distribution pattern of the Bale monkeys has to bernstudied in the neighbouring Bale Mountains Massif as well. Results from suchrnfuture studies combined with these obtained in the present study could contributernin preparing proper management and conservation plans for the Bale monkeys.rnThus, appropriate management action should be taken to conserve the speciesrnand their most important food resources, bamboo.rnKey words: Bale monkey, diet, distribution, Ethiopia, habitat preference,rnhome range, Odobullu Forest, population size