Animal vision

[homer]

I've heard that many animals are colour-blind. Is it true, and how do we know?

[Lord Panda]

In the past I have heard that (a) dogs see in black and white and shades of grey and (b) bulls are colour blind, but I confess I have no idea how they found this out!

[horseman]

Generalisation here, but'.there is often a misconception in the use of the term 'colour blind'. People tend to think that colour blind means 'black and white' but this isn't quite the same thing. Humans can see reds, blues and greens. Usually animals can only see blues and reds - or blues and greens - but not all three together. So they can still see colours. They aren't getting an image like we would see on a black and white TV ' rather like a TV on which the colours are distorted. So they do see colour ' just not as perfectly defined as we see it.

[Lord Panda]

Just remembered - the light reception the the back of their eyeballs works differently from that in humans.

[Sensei]

One way of finding out if animals see color is to shine a pure color in their eyes and see if the brain responds. I've tried red light from a fairly bright LED on a cat and the cat's pupils didn't contract at all (the same way paramedics shine a flashlight in your eyes to check for dialation), so I assume that means that that is one way of telling if an animal can see color. For what it's worth, I've seen ads in hunting magizines that sell products to block UV from reflecting off your clothing because deer can see it. I don't hunt, so I have no idea if this is true.

[Ginbottle]

Horses can see colour because if they couldn't, they would refuse the fence.

[twinkle toes]

Just because a horse refuses a fence does not mean that he is colour blind, it is more likely to be the shape and height of the obstacle that puts him off.

[bubba_skinny]

just as they hear in a different frequency range of humans, there vision picks up a different part of the light spectrum

[KEJ2000]

This is a fact: The human retina contains two types of cells, rods and cones. Cones perceive colour while rods perceive black and white. The retinas of dogs, etc., have been analysed on a cellular level and found to contain only rods. A textbook on [Visual] Perception will give you the same answer!