Gelada is the only survivor of the genus Theropithecus, which once included several successfulrnextinct species that lived in Africa and Asia. The wild populations of gelada are now restrictedrnonly to the Ethiopian plateau. The present investigation deals with population structure,rnbehavioural ecology and habitat vulnerability analysis of gelada (Theropithecus gelada)rnpopulation in Guassa Community Protected Area, Ethiopia. To collect data on populationrnstructure and behavioural ecology, three units were identified from six bands of geladas. Inrnorder to examine the social bonds among geladas, a total of 2,467 grooming interactions in 320rnhours of grooming bouts were extracted from the data set. A total of 7, 890 and 6,250 feedingrnrecords were obtained from scan sampling during wet and dry seasons, respectively. Nutritivernvalue of food plants of geladas was determined. For habitat vulnerability analysis, land-coverrndata from Landsat images of 1986, 2002 and 2013 were used. Structured interviews and grouprndiscussions were held with the local people to assess their attitude towards gelada and thernprotected area. The mean number of females per harem varied from 4.1 to 7.1 for the sixrnstudied bands. The sex ratio (females per males), the adult sex ratio and the mean number ofrnreproductive females within the units were not statistically significant between seasons (P >rn0.05). In the study bands, there was an overall increase of the population by 17.1 % per annum.rnThe mean annual mortality rate of geladas was 1.4 %. Geladas spent significantly more time inrnforaging and moving during the dry season compared to the wet season, whereas the time spentrnin grooming, playing and resting were significantly more during the wet season. The foodrnplants of geladas were better in protein, crude fibre and neutral detergent fibre constituents, butrnpoor in fat. Change detection matrices revealed that within a representative subset of the studyrnarea, grassland, Helichrysum, farmland and shrubland have decreased from their previousrnextent of cover, whereas extents of forest and Erica have increased. The difference in the unitrnsize and variations in time spent on activity patterns of geladas between seasons were related tornseasonal variability. The extent of grassland, Helichrysum and shrubland decreased during thernperiod 1986 - 2013. This might be due to human induced and ecological process, whereas thernextents of forest and Erica have increased, which might be correlated with the increasing forestrnconservation efforts in the area. This investigation provides useful information on geladarnpopulation structure, habitat changes and attitude of local community towards gelada and theirrnconservation in the study area.rnKeywords: Behaviour, band, community participation, geladas, Guassa, habitat changerndetection, land-use/land-cover changes, population structure, nutritive value