Table of Contents:
- The Anatomy of a Dog’s Eye
- Why Do Dogs Eyes Glow in the Dark?
- Canine Night Vision vs. Feline Night Vision
- Can Dogs See in Color?
Our dogs have some pretty spectacular sensory powers. While our ears can only hear sounds below 20,000 Hertz, theirs are strong enough to detect tones as high as 65,000 Hz. Their snouts have 300 million scent receptors (50 times more than the average human nose) and are capable of sniffing out the equivalent of a single drop of water in 20 swimming pools.
A dog’s eyes are impressive too. Today’s canines evolved from crepuscular wolves, predators who hunted and were most active during periods of low light. They’ve inherited the ability to see in the dark and navigate easily through dim conditions.
The Anatomy of a Dog’s Eye
The secret to a dog’s night vision begins at the pupil. Canine pupils — like feline pupils and those of other mammals — are much larger than ours, allowing more light to reach the retina. As in the human eye, canine retinas include two different types of light receptors: rods and cones. Cones are sensitive to color, bright lights, and fine detail, while rods are sensitive to motion and provide for vision in dim light. Dogs have more rods in their eyes than humans and, as a result, they’re more sensitive to changes in motion and better able to see in the dark.
Beneath a dog’s retina is a reflective layer called the tapetum lucidum. Reflecting light back into the eye, the mirror-like layer provides another opportunity to register images. While dogs can’t see in pitch-black conditions, the combination of a rod-dominant retina and the tapetum lucidum makes near darkness no match for a dog’s powers of sight.
Why Do Dogs Eyes Glow in the Dark?
You may not have heard about the tapetum lucidum, but you’ve probably seen it. Have you ever been startled to see your dog’s eerie, yellow-green eyes staring from across a darkened room, or wondered why your pooch’s eyes glow in photos? No, your dog isn’t possessed, their eyes are just functioning normally. That shining quality comes from light bouncing off of the tapetum lucidum. As many a startled cat owner can attest, feline eyes include these reflective layers as well.
Canine Night Vision vs. Feline Night Vision
When it comes to night vision, cats are the top dog. In addition to a tapetum lucidum and an abundance of rods, a cat’s eye has a large, elliptical cornea. This allows an especially large amount of light to enter the eye and reflect against the tapetum lucidum. How powerful is a cat’s vision? They need just one-sixth the amount of light that we do.
Can Dogs See in Color?
Sort of. While a dog can’t fully appreciate the rainbow, the popular idea that canines see in black and white is a misconception. Like some color-blind humans, dogs’ retinas lack the cones necessary to perceive shades of red and green. Dogs are capable of seeing yellow, blue, and combinations of these colors. Research suggests that this results in a visual world that’s mostly composed of different grays and browns.
Don’t be surprised if your pup responds more strongly to yellow or blue toys than to others.