Color vision in sika deer (Cervus nippon) : color discrimination between the three primary colors (red, green, and blue)

[Summary] The ability of two sika deer (Cervus nippon nippon) to discriminate between the three primary colors (red, green, and blue) under both light and dark conditions (Experiment 1 and Experiment 2) was surveyed using a T-maze technique. The light intensity in the center of a stimulus color card in experiment 1 was 200 lux and that in experiment 2 was 0.1 lux. One session consisted of 20 trials. The criterion of successful color discrimination was 16 or more correct choices out of 20 trials for 3 sessions in a row (P < 0.01 by Chi-square test) . Experiment 1 : both sika deer fulfilled the criterion in the 3rd and 4th sessions in the discrimination test among the three colors. Experiment 2 : The proportion of correct responses of two sika deer reached the criterion within the 8th session in red (the positive stimuli) vs. another color ; green and blue (the negative stimuli) discrimination tests. In each of the green vs. blue, green vs. red, blue vs. red, and blue vs. green discrimination tests, the two sika deer reached the criterion by the 4th session. In conclusion, sika deer did possess the ability to discriminate between the three primary colors (red, green, and blue) under both light and dark conditions.