Individual variations in color vision among squirrel monkeys (Saimiri sciureus) of different geographical origins.

A forced-choice discrimination procedure was used to test color vision and visual sensitivity in 10 squirrel monkeys (Saimiri sciureus) originating from three geographical locations (Bolivia, Colombia, Guyana). In agreement with results from an earlier study of vision in squirrel monkeys of Peruvian origin, striking individual variations in color vision were found among these squirrel monkeys. Some of these animals had trichromatic color vision, while others were dichromats. Within these two categories, a total of five color vision phenotypes could be discerned. Most of these types are qualitatively similar to common forms of human color-defective vision.