September 28, 2009 Photo taken from Square Ledge in Pinkham Notch
Photo: Nancy Ritger
After a stretch of perfect fall weather with cool nights and warm sunny days we see a full palate of fall colors across the landscape. The reds, oranges and yellows get me thinking that the seasons are changing once again and I really should make sure the wood is piled high and the garden put to bed before the winter winds blow. While I sit on top of Square Ledge in Pinkham Notch I have to wonder how many of these colors can animals see?
Starting with the human eye…. Humans have specialized cone and rod cells in the retina that detect color and light. Cones detect color while the rods allow us to see in dim light. In daylight the cones are forward on the retina enabling us to see color. As the light fades the rods move forward on the retina and cones retreat allowing us ability to see shapes and movement in low light rather than color.
To consider whether or not animals can see color we have to look at the eye structure. A general rule is that animals active in the daytime possess more cones to rods whereas animals active at night possess more rods. Many nocturnal animals have a larger proportion of rods to cones present in the eye enhancing their ability to see in low light. These animals rely on greater number of rods for extended night vision and keener detection of movement. They also have a tissue layer called the tapetum lucidum in the back of the eye that reflects light back through the retina, increasing the amount of light available for it to capture. If you ever notice the glow of an animal’s eye in your headlights at night it is the light reflecting off the tapetum lucidum. The human eye does not have a tapetum lucidum layer making it more difficult for us to see in low light conditions. Animals with more rods can see well in low light but they do not have the cones to see color in the same way humans can see color.
Humans can detect color in different wavelengths. Cones in the human eye detect red, blue and green wavelengths. Research shows that dog eyes’ have cones but they can’t distinguish between green and orange and a cat can see in color but reds look more like gray to a cat’s eye.
“Dr. Karl Miller, a recognized deer researcher from the University of Georgia, has studied deer vision extensively. According to the results of Miller's research, deer perceive color much as a human with red-green color blindness would. Their color vision is poor in the longer wavelengths. In light bright enough for color vision orange and red will be perceived by the deer as shades of dark yellow and colors in the shorter wavelengths of blue and purple can be perceived quite well by deer.”
In the insect world the compound eyes of honeybees enables them to see ultra-violet wavelengths beyond what humans can see.
So the long and short of whether or not animals can see the colors of fall is yes they can see color. They just may not perceive it the same way we do. The shifting colors in the forest signal the change of season to us, but animals are responding to changes in daylight, temperature and food supply rather than color to signify the change of seasons.
Thanks to: www.wisegeek.com