Habitat-related variation in daily activity patterns of Boutourlini’s blue monkey (Cercopithecus mitis boutourlinii) in Saja Forest, Kafa Biosphere Reserve, Southwest Ethiopia

Abstract Background Activity budgets provide insights into how primates respond to habitat variation. Through behavioural flexibility, primates, including blue monkeys, can adjust their activity patterns and resource use under changing environmental conditions. This study compared the activity budgets of two Boutourlini’s blue monkey groups inhabiting different forest zones of Saja Forest: the core and transition zones. We collected Behavioral data from August 2024 to October 2025 using the instantaneous scan sampling method. Results A total of 19,725 behavioral observations were recorded. Feeding was the dominant activity (29.6%), while times allocated for other activities were a smaller proportion (7.5%). The core-zone group spent significantly more time on feeding (33.0%), whereas those in the transition study group spent more time on movement (29.5%), and both showed statistically significant differences. Social activity was also higher in the transition zone group (13.5%), but it was not significant. Feeding was higher in the dry season (32.11%), whereas moving was higher in the wet season (28.67%). Diurnal patterns were observed, with feeding peaking in the morning and afternoon, while resting was highest at midday. Activity budgets varied among sex–age categories, with adult females showing the highest proportion of feeding activity (33.3%). Conclusions These findings provide baseline information on the activity budgets of two Boutourlini’s blue monkey groups occupying different forest zones. The observed variation in activity budgets between study groups and across seasons suggests behavioural flexibility under different environmental conditions. Future studies involving multiple independent groups per habitat type and direct measurements of habitat characteristics are needed to better understand the ecological factors influencing behavioural variation and to support conservation planning.