Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [97]-106).

Squirrels appear to be unique among sub-primate mammals in being able to see at least some colors. A readily available Oregon squirrel species, golden mantled ground squirrels (Citellus lateralis), which has not previously been tested under laboratory conditions for color vision, was subjected to color discrimination testing in a Skinner box. On the basis of recent physiological tests of color reception capacity and behavioral tests of color discrimination response in closely related species, it was predicted that this species should be able to discriminate blue, green and possibly yellow, but not red. Three experiments were conducted. The first, a pilot study, checked for discrimination of blue from green and blue from gray; subjects were rewarded for pressing on one color, shocked for pressing on the other color. The second experiment, the main part of the study, used one subject tor each of three discriminations: green from gray, yellow from gray, and red from gray. Here, a choice approach was employed: two bars were used, with subjects having to choose the correct one tor each stimulus, receiving a food reward for correct choices and no reward for incorrect choices. Third, a series of tests was devised to check for use of cues other than color as a possible basis for discrimination in the main experiment. These squirrels succeeded in discriminating all four colors, and results of the series of cue tests indicate they were not making significant use of non-color cues. Despite past results, therefore, it was concluded that this species is capable of seeing all colors in the visible spectrum. This result should be of interest to evolutionary theorists and may have important implications for current theories of color vision processes.