Melin, A. D., Fedigan, L. M., Hiramatsu, C., Sendall, C. and Kawamura, S. (2007). Effects of colour vision phenotype on insect capture by a free-ranging population of white-faced capuchins (Cebus capucinus). Animal Behaviour, 73 (1): 205-214. ScienceNOW Daily News, 9 January 2007. DISCOVER, 2 April 2007.

We evaluated whether dichromatic capuchin monkeys (Cebus capucinus) were more efficient than trichromatic monkeys at capturing camouflaged and non-camouflaged insects. Through fecal DNA analysis, we determined the genotypes of the M/LWS opsins for 34 capuchins in two groups inhabiting Santa Rosa National Park, Costa Rica. Dichromatic monkeys were more efficient at detecting camouflaged, surface-dwelling insects, especially under conditions of low ambient light. However, unexpectedly, trichromats were more efficient in extracting embedded, non-camouflaged, insects from substrates. To our knowledge, this is the first study to document a foraging advantage to dichromatic monkeys in the wild. Our findings show that there is a lack of heterozygote advantage in foraging for surface-dwelling insects and therefore indicate this mechanism may not be the sole driving force maintaining polymorphic colour vision in this population.