Friday, 30 October 2015

deer in the garden - what do deer see?

I see the deer in the garden more often now. A few days ago the group of deer paused so I could get a look at them and there was a large one which is probably the one I saw several days ago which was assumed to be a cougar.  They can apparently see me inside at dawn even though I only have a lamp and the computer light.

The Study
In August 1992, a group of leading deer researchers and vision scientists gathered at The University of Georgia (UGA) in Athens to conduct this landmark study. The group of researchers included Drs. R. Larry Marchinton and Karl V. Miller, and myself from UGA, Dr. Gerald H. Jacobs and Jess Degan from the University of California, and Dr. Jay Neitz from the Medical College of Wisconsin. This study was made possible due to a highly sophisticated computer system developed by Dr. Jacobs. This system is based on the principle that an electrical response is produced when light enters the eye. The computer interprets these responses and translates them into a “scientific best guess” of what deer can actually see.
Findings of the Study
The results of our study confirmed that deer possess two (rather than three as in humans) types of cones allowing limited color vision (Figure 1). The cone that deer lack is the “red” cone, or the one sensitive to long wavelength colors such as red and orange. This suggests that wearing bright colors while hunting does not affect hunting success. This does not mean that these colors are invisible to deer, but rather that they are perceived differently.
Deer are essentially red-green color blind like some humans. Their color vision is limited to the short (blue) and middle (green) wavelength colors. As a result, deer likely can distinguish blue from red, but not green from red, or orange from red. Therefore, it appears that hunters would be equally suited wearing green, red, or orange clothing but perhaps slightly disadvantaged wearing blue.
The results regarding the UV capabilities of deer were equally fascinating. Our results confirmed that deer lack a UV filter in their eye and that their vision in the shorter wavelengths was much better than ours. Deer also were found to have a relatively high sensitivity (good vision) in the short wavelengths where UV brighteners and dyes are active.
While not entirely conclusive, this finding suggests that deer are capable of seeing some UV light and that fabrics containing UV dyes and brighteners may be more visible to deer than to humans.