Dogs are red-green colour blind, research indicates
Dogs are colourblind and struggle to distinguish between red and green, meaning finding a red ball in the park could prove tricky, scientists have said.
Experts have known for some time that dogs have poor vision, and are up to eight times worse than humans at seeing things in detail. But until now, nobody knew why.
Now scientists have developed a test for dogs and found that they struggle to tell red and green apart, much like colour blind humans, a condition known as deuteranopia.
In the wild, dogs are a crepuscular species, meaning they are most active in dawn or dusk, for which colour vision is not needed. But through domestication, pets are awake mostly in the daytime, for which their eyes have not yet evolved.
Dr Marcello Siniscalchi, of the department of veterinary medicine at the Univesity of Bari in Italy, said dog trainers may want to avoid red clothing or shoes if working on grass, because animals will struggle to see their movements.
“Overall, the direct demonstration that dogs are red-green colour blind is not only important for people directly involved in dog training but also for owners who want to improve their dog's attentive skills during some activities such as play that is at the heart of a healthy owner-dog relationship,” he added.
“If at the park you want to get your dog to catch a flying Frisbee or to bring back a ball falling on the green grass it would be better if you thought of using blue instead of red toys.”
The researchers using a modified test of colour vision in humans, known as Ishihara's test, where numbers are hidden in a circle of red and green dots.
People who are red-green colourblind cannot see the numbers. For the new test, the researchers developed a similar experiment, but used the image of cat instead of numbers.
“We show that dogs exhibit a behavioural response similar to that of red–green blind human subjects suggesting that dogs struggle to distinguish between red and green colours,” added Dr Siniscalchi.
“It would be reasonable to hypothesise that dogs also have difficulty in discriminating between brown and orange but we have not directly tested these colour shades.
"Besides contributing to increasing the knowledge about the perceptual ability of dogs, the present work describes for the first time a method that can be used to assess colour vision in the animal kingdom.”
The research was published in the Royal Society journal Open Science in the UK.