Population structure and feeding ecology of Guereza (Colobus guereza) in Borena-Sayint National Park, northern Ethiopia

Abstract

Population size, structure, activity time budget and feeding behavior of Guereza (Colobus guereza) were studied in Borena-Sayint National Park (BSNP), Ethiopia, from August 2008 to March 2009. Line transect survey technique was applied to investigate the population size and structure. Guerezas were observed only in the forest habitat. The mean group size, group density and group encounter rate in the forest habitat were 7.7 individuals, 14.8 groups per km2 and 1.43 groups per km, respectively. In addition, the majority of the groups contained one adult male. The total population was estimated to be 2170 individuals. The population was skewed towards females. The ratio of male to female, young to adult and infant to female were 1.0:1.45, 1.0:4.16 and 1.0:4.9, respectively. The age structure was 47.9% adult, 32.7% sub-adult, 11.5% young, and 7.9% infant. No significant variation was observed in group size between seasons. Guereza consumed 31 plant species which consisted of 15 trees, 12 shrubs and 4 herbs. Dombeya torrida and Olinia rochetiana were the most consumed plant species which accounted for 18.2 and 12.6% of the diet of guereza. Leaves comprised of the largest proportion of the food items consumed (71.6%). Their diurnal activity is dominated by resting periods. This study contributes greatly to add information on the status of guereza in Ethiopia, and for its conservation and management. Key words: Activity, age structure, Borena-Sayint, diet, guereza.