Antelope ground squirrels (Citellus leucurus) were able, after conditioning, to respond correctly to a port illuminated with light at a wavelength of 460 nanometers. This color randomly presented at one of two positions, was correctly selected in reference to a second port illuminated with light at 500, 520, 569, and 600 nanometers, or with white light of varying intensity. Luminosity was not a factor in the discrimination.