During walks with our dog, we are amazed at her visual performance in the dark. She is a relatively old Newfoundland and we are not confident that she can see brightly in the daylight. However, when in the woods late in the evening she always leads and drags us to places where we don’t find quite comfortable.
So, it got us wondering, do dogs see in the dark. We all know that cats excel at the nocturnal vision, but what about dogs?
How good can dogs see in low light?
Dogs are better at night vision than humans are. We did not find reliable sources to put a number on it. Science Daily, for example, states that dogs “can probably see in a light five times dimmer” than humans can. However, the word “probably” makes it sound unconvincing. Especially that the scientist they quote in his own literature review (section “sensitivity to light”) does not mention this “five times dimmer” threshold.
It does state that cats can see in a light six times lower than humans and puts dogs on probabilistic terms that they are slightly worse. In fact, despite cats being tested for the brightness threshold several times, we could not find a published study attempting the same on dogs. Strange.
However, while there isn’t really a number to state, it is correct to say, that the dogs’ ability to see in dim light is better than humans but not as good as cats.
Do not underestimate dogs’ abilities though. Above probably means that dogs can still see in the conditions that humans would describe as pitch black. This is why our dog bravely drags us through the darkest parts of the wood where we wouldn’t go on our own. But how do dogs do that?
How do dogs do it?
The answer wouldn’t be surprisingly different from what we know about cats. Dogs’ eyes are well adapted to gather and use the tiniest amount of light available.
- Tapetum lucidum is the largest contributor. The name comes from Latin and means bright tapestry. It is a layer at the far end of the eyeball, just beside the retina. Tapetum reflects the light that has passed through the retina back to it, so it receives more light. Unfortunately, this also means that the light gets scattered and dogs have lower acuity than we do. Think about drawing with light pencil strokes. If you’d draw over the existing image again, it would be easier to see, yet, might get distorted. This is why dogs do not have so good acuity, yet it still better than that of cats, who pay more for even better nocturnal vision.
- Large pupils is also a trait that lets your dog enjoy the sight in low light conditions. The size matters and the larger the iris, the more light it lets in. Similarly, if you’d want to get a photo camera, a larger lens would get you better pictures. And, if you prefer a telescope, a greater diameter of the tube will get you more stars.
- More rods in the central part of the dog’s retina. The basic is that cones are useful in color discrimination and rods in vision in lower light. The human retina consists of mostly rods, hence, we are good with colors, but suck at nocturnal vision. The retina of cats, on the other hand, has even more rods than dogs do.
Besides these, we’re sure there are more minor adaptations that make the eye of a dog superior in low light conditions when compared to human eyes. Don’t feel sad though, our acuity is significantly better, just as we are better with colors and our binocular vision, thus the depth perception is way superior to that of dogs.
The endnote, dogs do see rather well in the dark. We could say that dogs when it comes to vision, are somewhere between humans and cats. Not only in the ability to see in the dark, but in other aspects as well.
