Effect of color vision phenotype on the foraging of wild white-faced capuchins, Cebus capucinus

New World monkeys exhibit a color vision polymorphism. It resultsfrom allelic variation of the single-locus middle-to-long wavelengthopsin gene on the X chromosome. Females that are heterozygousfor the gene possess trichromatic vision. All other individualspossess dichromatic vision. The prevailing hypothesis for themaintenance of the color vision polymorphism is through a consistentfitness advantage to heterozygous trichromatic females. Suchfemales are predicted to be more efficient than dichromats whendetecting and selecting fruit. Recent experiments with captivecallitrichid primates provided support for this hypothesis bydemonstrating that color vision phenotype affects behavioralresponses to contrived food targets. Yet, the assumptions thattrichromatic females acquire more calories from fruit, or thatnumber of offspring is linked to caloric intake, remain untested.Here, we assess if, in the wild, heterozygous trichromatic individualsin a group of white-faced capuchins (Cebus capucinus) enjoyan energetic advantage over dichromats when foraging on fruit.Contrary to the assumptions of previous theoretical and experimentalstudies, our analysis of C. capucinus foraging behavior showsthat trichromats do not differ from dichromats in their fruitor energy acquisition rates. For white-faced capuchins, theadvantage of trichromatic vision may be related to the detectionof predators, animal prey, or fruit under mesopic conditions.This result demonstrates the importance of using a fitness currencythat is relevant to individual animals to test evolutionaryhypotheses.