There are three main reasons why some animals can see better than humans can at night. The first reason is that their eyes, relative to body size, are larger and can gather more light than human eyes can. More light results in a brighter image.

The next reason has to do with the rods and cones in the nocturnal animal’s eyes. Cones are used for detail and work best in bright light. A nocturnal animal has little need for the color vision provided by the cones and therefore has more room for the rods that detect general information such as motion and shapes.

The third reason why nocturnal eyes excel in the absence of light is due to the tapetum lucidum, a membrane on the back of the retina that reflects light back to the retina to double the retina’s exposure to light. The reflective tapetum can be seen in the light reflected back out of animals’ eyes at night when you shine a flashlight on them.