Intra- and Interannual Variation in the Fruit Diet of Wild Capuchins: Impact of Plant Phenology

Abstract

Understanding primate diet plasticity and what causes foraging variation is crucial to understanding their ecology and evolution. Foraging choices are limited by food availability, and primate diets may shift within and between years. How primates respond to interannual variation and the extent of their dietary flexibility are poorly known. White-faced capuchins (Cebus capucinus imitator) have a diverse diet and are informative study subjects for investigating dietary shifts in response to environmental variation. We investigate the phenological characteristics of plant foods and calculate monthly fruit production and probability of fruiting for each dietary species and report on how capuchin foraging varies intra- and interan- nually. We compare the dietary importance of foods consumed over two 1 year-long sampling periods. Finally, we determine how food use changes seasonally by com- paring biweekly diet variation. Most plant food species examined produce fruit sea- sonally, although two important species are aseasonal. The overall biomass of capuchin fruit foods varies considerably monthly and annually. During scan sam- pling, capuchins were observed to consume 90 different plant food species across 24 months of study. Almost half of these plant foods were only consumed during one of the two study years, but such foods accounted for only 10% of the plant diet. Within 2-week periods, capuchins were typically reliant on one or two plant foods (i.e., >50% of the diet for that period), but few plant foods were important for mul- tiple periods. This study illustrates the importance of studying both food and forag- ing characteristics at different scales and demonstrates the necessity of long-term projects for interpreting foraging behaviour.