Research on Simple Visual Discrimination Abilities of the Giant Panda
Recent research by the Zoological Society of San Diego (ZSSD) on giant panda chemical communication has greatly increased our understanding of this aspect of giant panda sensory perception. Other sensory systems have not yet been investigated, and almost nothing is known about the visual abilities of pandas. Although giant pandas do not seem to have need for a highly developed visual system, most diurnal mammals, including other bear species, are postulated to have at least some level of color vision. The eye of the giant panda contains rods and cones, with the rods outnumbering cones. This suggests, but does not guarantee, that giant pandas possess acute night vision and are capable of color vision. Experimental testing of black bears has shown that these animals are able to discriminate green and blue. The purpose of this study was to use methodology similar to that used to test black bears to determine if giant pandas were capable of discriminating colors.
The two giant pandas on loan to Zoo Atlanta were study subjects. This study consisted of two phases. The first phase was conducted to gather empirical evidence that giant pandas can be trained using operant conditioning to respond to the test apparatus, and that they can learn visual discrimination. The second phase of this study was used to determine if giant pandas are able to distinguish colors. In phase one, the stimuli were the 18 shades of gray, including white and black. In phase two, the stimuli were 5 shades of each color, green, blue, and red, which were compared with the gray stimuli.
Both pandas were able to discriminate the white stimulus from two gray stimuli (male in 317 trials, female in 250 trials), and the black stimulus from one gray stimulus (male in 824 trials, female in 822 trials). In addition, both pandas were able to discriminate green-versus-gray stimuli (male 759 trials, female 860 trials) and red-versus-gray stimuli (male in 120 trials, female in 560). The female was also able to discriminate blue-versus-gray stimuli (in 405 trials). The male was not tested on this color. For most of the testing, the male had higher than chance performance throughout, whereas female’s performance was more variable and often dipped below chance. Neither subject consistently learned faster than the other, but the male showed some tendency of the “learning to learn phenomenon,” as evidenced by his extremely rapid discrimination of red versus two grays
Giant pandas were able to discriminate shades of red, green and blue stimuli from numerous shades of gray. Because brightness was eliminated as a cue, these discriminations can be attributed to color vision. Therefore, the present study provides experimental evidence that giant panda visual abilities, including color vision, are comparable to those of other bears and other non-nocturnal carnivores. Giant pandas, like other carnivores that have been studied, are most likely dichromats. The discovery of a neutral point, which is the identifying trait of dichromatic vision, would confirm this claim. In addition, further behavioral tests should be performed to identify if giant pandas fail to discriminate bluish-green stimuli from grays in order to fully explore the limits of giant panda color vision. The testing procedure developed in this study also allows for expansion into olfactory and auditory modalities. It has been found for many species that performance on discrimination tasks is confounded by their dominant sensory modality. Therefore, using this procedure to measure other sensory modalities in giant pandas could help identify the giant panda’s dominant modality.