Toni Shelbourne explores the canine senses – this month, a look at the eyes…
Canine vision is vastly different from our human sight. Let’s start with colour perception. Very simply put, dogs have more rods than cones, which supports night vision. However, this has a detrimental effect on the range of colours they can see. Blue and yellow are the two primary colours dogs can detect. This is called dichromatic vision; we have a trichromatic vision, which includes the full-colour spectrum. Due to this limited range, they can struggle as many colours look similar. Put this in the context of finding a red or orange toy on green grass — without the movement you can see why he may strain to find the toy when it appears to be right under his nose!
The positive flip side of limited colour perception is that dogs can detect light six times dimmer than humans, giving them vastly superior night vision. This is assisted by a special reflective tissue at the back of the eye called the Tapetum Lucidum, which reflects light back into the retina; dogs effectively benefit from the same light twice. The downside to this feature is it reduces visual resolution in the day, so dogs’ sight has less acuity. They have a comprised ability to distinguish depth and the detail of objects; things can appear blurry at a distance. In short, the canine superpower of night vision has a direct negative influence on how well they see during the day.
Studies show that dogs, like us, can be short or long-sighted, the breed can also influence this, of course. They have binocular vision, seeing out in front of them and can detect movement exceptionally well.
Why should we take note of the canine sight differences? It could affect how we interact, manage, and train our dogs. Firstly, think about how their compromised daytime vision may impact anxious and fearful dogs. Your dog could react if a perceived threat is moving towards him, but he cannot quite make it out. Think about dogs who seem to bark at a familiar person approaching, but suddenly flip from barking to a happy and excited body posture when the person speaks, and th
