| White-faced capuchins are among the many species of neotropical primates possessing polymorphic colour vision. Several theories have been proposed to explain the evolution and persistence of multiple trichromat and dichromat phenotypes. Currently, most researchers attribute this polymorphism to a heterozygote advantage to trichromats while foraging. In my research, I tested whether dichromacy was more suited than trichromacy for any of the foraging tasks capuchins regularly encounter. I also looked for evidence of niche divergence in diet or for preferred foraging conditions in the forest among individuals with different colour vision phenotypes. I did not find strong support for the theory of niche divergence. However, I did find that dichromats were more efficient than trichromats at catching camouflaged insects. While trichromacy is likely beneficial for finding certain foods, my results demonstrate that dichromatic monkeys have an advantage for other foraging tasks, which suggests a form of frequency-dependent selection. |
