How Dogs See – Pet tip 117
Through a dog’s eyes, the world is a very different place: every fire hydrant is a toilet, every shoe is a chew toy, and every person is a ticket to kibble and treats. Though this is perhaps a bit of an oversimplification, there are some real differences between the way humans and dogs perceive the visual world. In an attempt to better understand our canine companions, it is worth while to consider some of these differences and how they might affect the way we interact with our pets.
As humans, we rely heavily on our vision. Imagine trying to run your daily errands with your eyes closed! Dogs, on the other hand, use their sight in combination with an acute sense of smell and impeccable hearing. It makes sense then that their vision need not be quite as accurate as ours. It is estimated that in terms of discerning details, dogs’ vision is roughly five times poorer than that of humans. Where a person might be able to distinguish an object that is 90ft away, your dog would likely need to be within 20ft to see the same object. Also, the spectrum of colours visible to dogs is much less than what we can see. Essentially they see the world in two main hues of blue and yellow. They are unable to differentiate between the colours green, blue, red, and orange, and actually are not so different from people who are colour blind.
The visual capability of canines also pales in comparison to that of humans when it comes to depth perception. This feature of human vision stems from the fact that our visual fields overlap significantly in the centre. This isn’t the case for dogs, whose eyes are positioned more laterally on the sides of their heads. Obviously eye positioning depends somewhat on breed, but when compared to humans, depth perception amongst all dogs is poor.
While human vision obviously surpasses that of dogs in many ways, there are also a number of ways in which dogs’ vision is superior. The most notable of these is their night vision. Dogs (and many other animals besides humans) possess a surface at the very back of their eyes called the tapetum lucidum. This structure acts to reflect light back out through dogs’ eyes allowing them to navigate more clearly in the dark (it’s also the reason your dog’s eyes might look like they have an eerie glow sometimes at night, and why almost every picture of your dog comes out with red-eye).
Dogs also have other visual adaptations which humans lack, most of which seem to be related to hunting abilities. For example, dogs have a particular sensitivity to motion. They are able to detect the motion of an object or other animal up to 900 metres away! Dogs also have excellent peripheral vision. People can see roughly 180 degrees around themselves at any time, whereas a dog’s field of vision can range up to 250 degrees. This again is related to the lateral position of their eyes.
It would be unfair then, to say that dogs do not see as well as humans. While their ability to distinguish details and colour is notably less than ours, these are not feature which have been important to their species over time. Instead, dogs have developed predatory adaptations throughout evolution which humans obviously lack. Undoubtedly, there are many more intricacies to the canine visual world that we as humans have yet to discover. After all, it is impossible for us to describe their vision beyond the realm of what we ourselves can see. So the next time you catch your dog staring off seemingly into space, remember that his visual world is different from mine and yours. By accepting these differences we can all better understand and appreciate the dogs in our lives.
Alison Norwich – Pets.ca writer