Why do animals have luminous eyes at night?
The eyes of many animals, but not humans, contain a reflective layer called the “tapetum lucidum”. That helps the eye gather more light, which improves night vision. You just see what’s reflected back at you; the rest of the light is absorbed by the creature’s eye. But it’s not a precision mirror, and it tends to give you less accurate vision during the day. Humans go in for precision (which is why we can read) at the expense of hunting or seeing predators at night. The tapetum lucidum is reflective, but it’s not like a mirror. It’s more like some bird feathers and butterfly wings, where it uses ridges or dots of clear material to achieve a colored effect. The distance between the ridges interacts with the frequency of light to give you different colors. The colors you’re not seeing are the ones that the animal are what the animal actually sees. If you want to know way too much more, read the article from Veterinary Opthamology below. Sources:
