The perception of color by cattle and its influence on behavior.

Experiments have suggested that cattle can only discriminate long wavelengths of light (colored red) from short (blue) or medium (green) wavelengths, and not short from medium wavelengths; however, stimuli were inadequately balanced for intensity. In this study, an initial group of calves was trained to discriminate light sources by intensity, and the intensities of short, medium, and long wavelength lights were then varied to determine when the calves perceived them to be isoluminant. A new group of calves was tested for their ability to discriminate between the three isoluminant sources and were able to discriminate between long and short or medium wavelengths (mean correct choice 82 and 89%, respectively) but had limited ability to discriminate between the short and medium wavelengths (three out of seven calves could just discriminate in the first eight tests, but thereafter they all selected at random). The response to three stimuli--novel, fearful, and their handler--was video-recorded in isoluminant short, medium, and long wavelengths and movement was assessed by image analysis. In the fear test (a loud noise behind them), the calves negotiated a barrier and concealed themselves more rapidly in the medium (58 s) than the short wavelength (95 s) light. They performed fewest movements in the medium wavelength light compared with the short and long wavelength lights in the novel stimulus and fear tests. They had stronger movement in the long than the short or medium wavelength light in the novel arena test and in response to the handler, and they took least time to reach the handler in the long wavelength.