Preliminary evidence for color stimuli discrimination in the Asian small-clawed otter (Aonyx cinerea).

Color discrimination ability can be determined through anatomy or perceptual ability. In this study we tested perceptual ability. Three Asian small-clawed otters (Aonyx cinerea), one male and two females, were trained via operant conditioning to discriminate stimuli within a training task. If they passed criteria for this task, they were tested on as many as six delayed matching-to-sample experimental tasks. These experimental tasks involved comparing varying saturations of the colors blue, green, and red against varying shades of gray, as well as against each other. The male reached criterion on five of the experimental tasks, indicating an ability to discriminate the stimuli. One female participated in only two tasks and did not achieve the criteria as set. The second female did not pass the training task, and thus was not experimentally tested. This study overall showed some early evidence that Asian small-clawed otters may have the ability to learn to discriminate different stimuli on the basis of color cues. Sensory studies conducted on two other otter species and the results of this study indicate that color vision may be a common trait across Lutrinae species.