Can Your Dog See That New Red Ball?
It is a common belief that dogs are colourblind, in the sense that they see the world only in black, white and shades of grey. It is true that the range of colour a dog sees is much more limited and less intense than the colours that we humans see, they can still see colours though, but mainly blues and yellows and varying shades of grey.
The eyes of both people and dogs contain special light catching cells called ‘cones’ that respond to colour. Dogs have fewer cones than humans which suggests that their colour vision won’t be as rich or intense as ours. However, the trick to seeing colour is not just having cones, but having several different types of cones, each tuned to different wavelengths of light. Humans have three different kinds of cones for colour detecting and the combined activity of these gives humans their full range of colour vision whereas dogs have only two types.
This is how the spectrum appears to dogs as opposed to people:
Dogs do not rely only on colour information to discriminate between objects. They also analyse the brightness or darkness and density to pinpoint an object. However, due to a dog’s extreme farsightedness putting objects that are near to them, slightly out of focus, colour vision is still very useful to them. From my own observations, my dog can spot a motionless squirrel a few meters away or several hundred meters away, by using their unique combination of powerful senses.
When it comes to night vision though, the tables are definitely turned! A dog’s night or dim-light vision is thought to be FIVE times better than humans! The dog’s larger pupil lets in more light and the centre of the retina has more of the light sensitive cells (rods), which work better in dim light than the colour detecting cones. You have seen how a dog’s eyes glow at night when you shine a light at them, this is because of the mirror like structure called the ‘tapetum’ which gives the dog a big advantage. It reflects light, and effectively gives the retina a second chance to register any light that has entered the eye.
Remember, when you throw that red ball on the green grass for them, colour-wise, it won’t stand out as well for them as it does for you, but your dog will be able to use their other amazing senses to help them find it anyway!
By Zoe Vanderbilt B.Sc