Dichromacy in the Ground Squirrel

Abstract

IN studying vision it has often proved informative to use situations in which less than the total visual system is operative. One way of achieving this for colour vision is by examining systems in which cones are the sole visual receptors. This is so rare in humans as to be effectively unavailable, but several other animals normally possess pure-cone retinas, and of these the ground squirrels have been of particular interest. Recent investigations¹ have indicated that at least some ground squirrels possess colour vision which is likely to be dichromatic. We have made measurements on two common species of ground squirrels that confirm these suggestions.