Seasonal niche shifts and foraging plasticity of the Southern Gelada (Theropithecus gelada obscurus Heuglin, 1863) (Cercopithecidae, Papionini) within the extreme Afro-alpine ecosystem of the Abune Yosef Zigit Community Conservation Area, Ethiopia

Understanding how primates adapt their foraging strategies to fluctuating environmental conditions is a central theme in behavioral ecology. The extreme Afro-alpine ecosystem presents a unique setting to test predictions of Optimal Foraging Theory and the Fallback Food Hypothesis due to its severe seasonal shifts in resource availability. This study investigated the dietary composition, seasonal variation, food preferences (dietary selectivity), and foraging plasticity of the Southern Gelada ( Theropithecus gelada obscurus ) in the Abune Yosef Zigit Community Conservation Area, Ethiopia. Using instantaneous scan sampling and vegetation surveys across dry and wet seasons, we recorded 761 feeding records encompassing 25 food items. Forbs dominated the diet (55.7%), followed by grasses (42.7%), and insects (1.6%). Geladas exhibited a consistent bimodal feeding pattern but demonstrated pronounced seasonal niche shifts. In the dry season, they highly expanded their dietary breadth (Shannon H' = 2.31) and relied heavily on underground roots, aligning with fallback food strategies. In the wet season, the dietary niche narrowed (H' = 1.92), with greater reliance on grass blades and young shoots. Electivity indices revealed highly dynamic, context dependent selectivity rather than fixed preferences, with preference rankings shifting between seasons. These findings highlight the remarkable behavioral plasticity of geladas and underscore their ability to dynamically adjust foraging strategies to survive in extreme, highly seasonal environments.