Which senses do wild vervet monkeys (Chlorocebus pygerythrus) use to evaluate potential food?

Abstract Traditionally, primates have been considered primarily visual animals. However, studies across a variety of taxa suggest that, in the context of food evaluation, reliance on this sense might be more nuanced that previously thought, with dietary specialization and food item properties leading to differences in sensory prioritization. We assessed the use of sensory cues during food evaluation and food-related behaviors such as muzzle contact in two mixed-sex groups of wild vervet monkeys ( Chrorocebus pygerythrus ) over 5 months (N monkeys = 44). Using 18,868 food evaluation observations collected during 44 hr of focal samples, we found that vervets mainly used their sense of vision when evaluating food (96.8% of all instances). However, the relative usage of each sense varied with food category, and we observed that males used smell for bark inspection more frequently than females. We also found that juveniles used tactile inspection more often than adults. Performance of most food-related behaviors investigated (preparation and rejection) differed significantly according to food type but not between age classes or sexes. In addition, juveniles initiated muzzle contact more often than adults and females received muzzle contact more often than males did. We found overall low rejection rates of food items, suggesting that most food items were familiar to the vervets regardless of age and sex. These findings are in line with optimal foraging theory, according to which the food evaluation process should be adapted to the familiarity of food items, allowing individuals to maximize their intake of energy and critical nutrients, while minimizing the time and effort spent in food evaluation.