Dichromatic and trichromatic Callithrix geoffroyi differ in relative foraging ability for red-green color-camouflaged and non-camouflaged food

An advantage for trichromatic color vision in primates is shown by its presence in many lineages, but little attention has been paid to the potential disadvantages of trichromacy. Most New World monkey species are polymorphic for color vision, with both dichromats and trichromats present within a single population. We tested the foraging ability of trichromatic and dichromatic Geoffroy's marmosets (Callithrix geoffroyi) for colored cereal balls (Kix(R)) under conditions of red-green color camouflage (orange/green Kix(R) against an orange/green background) or lack of camouflage (Kix(R) same color as background) in a naturalized captive setting. In separate experiments designed to test foraging ability at long distances (< 6 m) and short distances (< 0.5 m), trichromats found significantly fewer Kix(R) under the camouflage condition than in the non-camouflage condition. In contrast, there is no difference in the ability of dichromats to detect color-camouflaged versus non-camouflaged Kix(R). There is no significant difference between dichromats and trichromats for either camouflaged or non-camouflaged Kix(R), though the power in the tests is low because of high individual variation. The results have clear implications for the foraging strategies of trichromatic marmosets. Differences in intensity of competition between trichromats and dichromats for items of food of different colors in relation to background may also have consequences for the foraging behavior of dichromats.