Ask The Biologist

Well, deer eyes have it. Our’s don’t.

QUESTION: This might seem like a dumb question, but I’ve always wondered why a deer’s eyes reflect light at night but humans’ don’t.

ANSWER: It’s not a dumb question at all. Deer, like many other mammals, have several adaptations that improve their ability to see in low light. One is a reflective layer of cells on the retina called the tapetum lucidum. When light hits the retina, some of it is absorbed by specialized cells called rods and cones that then transmit a message to the brain where it’s interpreted as a visual image. Light that passes by and strikes the tapetum in reflected back, giving the rods and cones a second chance at absorbing and transmitting the image. We see it as eye shine.

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