what color is eyeshine in different animals
Since the same light passes through the eye twice, it increases animalsâ ability to see in low light conditions. Animals with the brightest eyeshine generally have more rods (light receptors) and fewer cones (color receptors) in their retinas, so they trade better night vision for color-blindness. The color of eyeshine varies from species to species: Deer have white, yellow or green eyeshine with a silvery sheen. Most owls have orange or red. From house cats to mountain lions, felines have greenish-gold.
The tapetum lucidum tends to lie behind or within the retina. This specialized structure essentially reflects light to allow for another round of reabsorption into the eye. There are different types of tapeta in various groups of animals. For example, carnivores and some other creatures have a tapetum rich in crystals of a compound called guanine; this is called the tapetum lucidum cellulosum. A sea lion or walrus, by contrast, has a tapetum lucidum fibrosum, defined by fibers of collagen. The striking shine of an animal's eye in the glare of a flashlight or headlight reveals the reflective tapetum, with the color of the eyeshine -- yellow, green, blue and such -- varying between species.
Most cats have a tapetum lucidum that reflects a light that appears to be either yellow or green. The differences in the eye shine color reflected are caused by varying amounts of zinc or riboflavin in the iridescent tapetum itself. The amount of light reflected and the color of the light being reflected varies. Even cats within the same breed can have different reflected eye colors. Cats have riboflavin in their tapetum, unlike dogs who have zinc. Cats with blue eyes, whether white-coated or Siamese, typically lack a tapetum lucidum.