Deer have more cones and less rods than humans. They have no red-sensitive rods at all. They also have no ultraviolet filtration, so they see blue much more acu

Deer have more cones and less rods than humans. They have no red-sensitive rods at all. They also have no ultraviolet filtration, so they see blue much more acutely and pick up on UV-wavelength brighteners quite easily.