Abstract # 211:

Scheduled for Saturday, August 19, 2006 08:00 AM-08:15 AM: Session 20 (Regency East #3) Oral Presentation

Effects of Color Vision Phenotype on Insect Capture by Free-ranging White-Faced Capuchin Monkeys (Cebus capucinus) in Santa Rosa National Park, Costa Rica

A. Melin1, L. Fedigan1, C. Hiramatsu2 and S. Kawamura2
1Department of Anthropology, University of Calgary, 2500 University Avenue NW, Calgary, Alberta T2N 1N4, Canada, 2Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Japan
     Like many platyrrhine primates, white-faced capuchins (Cebus capucinus) are characterized by polymorphic color vision, which is enabled via multiple alleles for a single-locus, X-linked opsin. In combination with an autosomal opsin, this arrangement provides trichromatic vision to heterozygous females, whereas homozygous females and males are dichromats. Because trichromatic vision enables visual differentiation among red, orange, yellow and green, trichromacy may be advantageous for finding edible fruits or leaves among mature foliage. Currently most researchers attribute the evolution and maintenance of polymorphic color vision to trichromat (= heterozygote) advantage. However, dichromacy may be better for achromatic tasks, such as penetrating color camouflage, especially under low-light conditions. We evaluated whether dichromats were better able to capture camouflaged invertebrates. Through fecal analysis, we determined the genotypes for each individual (N = 35) in two groups of capuchins living in Santa Rosa National Park. Foraging data were collected for seven months, encompassing both wet and dry seasons. Insect capture rates were affected by foliage density, height in forest and time of day. Dichromatic monkeys were significantly more efficient at capturing surface-dwelling insects (repeated-measures ANOVA, p < 0.05), especially under conditions of low ambient light. However, trichromats were significantly more efficient in extracting embedded insects from substrates (Mann-Whitney U test, p < 0.05). Our findings do not support heterozygote advantage as the mechanism maintaining polymorphic color vision in this population.