The development of colour vision in animals

[Catherine]

Colour vision in animals is a topic that people have long wondered about. Too often we have believed that animals, especially dogs have simple black and white vision. An article that I found makes the point that the world is full of colours and those colours are mostly not there for our benefit. Animals have very complex vision and colour plays an important role. How that colour vision developed is a fascinating area of study. We don't have all the answers, but we are definitely learning.

https://www.wired.com/story/evolution-color-vision/

I know insects have amazing colour vision. They can see things that we don't. Flowers that appear the same to us can look very different to a bee.
Now I wonder about reptiles.
Chameleons signal to each other through colour. A female will show certain colours when she is ready to breed. A male won't approach unless he see those colours. When she is pregnant she will look different and the male will leave her.

Snakes have amazing colours. They must see them or what would be the point. Do they allow snakes of the same species to find each other when they need to breed.  Snakes also rely on scent, but their colours are so incredible that they must serve a purpose.

I wonder if colour and colour vision evolved together?

[Tobi]

You bring up some interesting points. Colour in the animals' lives and on their bodies isn't there just for us to observe! It serves a purpose for them!
I have heard it said that dogs see better towards the blue end of the spectrum, and red/pink/orange shades seem grey-ish to them. But it's said that dogs see grass not green as we do, but a blue-ish shade.

I can't be sure if that is so, or not. The conclusions might be arrived at by examining colour-receptive features in the dog's eye structure. But the studies may have only been done in necropsy, and may not have been done on a large number of dogs. I don't know. Perhaps they chose colour blind dogs! Or selective breeding could affect colour vision for all we know. It can dramatically affect other aspects of a dog's physical structure and health.

My Jack Russell, Toby had an orange ball. My husband liked to eat a lot of fruit in the evening, and had a green apple, a red apple, a small grapefruit and an orange on the sofa next to him. These pieces of fruit were al about the same size, and coincidentally the same size as Toby's ball. Toby lost his ball, and started looking for it. After checking the floor, he jumped on the sofa, and went straight to the orange to sniff at that. Not the red apple, not the yellow grapefruit. The orange.

[Catherine]

I am sure dogs see colours. They may not see them exactly the way we do. We don't all see colours in the came way. I am not talking about colour blind people. They lack colour receptors or at least some colour receptors. Some people with colour vision do not seem to see the depth of colours. They see green as green. Some people can distinguish tiny variations in colours. A few drops of blue in the green makes it a whole different colour for them.

Maybe dogs are the same. Many dogs would have to be observed before we would know what they see. 
Clearly your Jack Russell, Toby could see orange and distinguish it from yellow and red. I can understand him not looking at the apples. They are different in shape, but the grapefruit is very much like and orange. He was going by the colour.

I think we have just scratched the surface of studying colour vision. The world is full of colour so it is safe to say that colour must have played a part in evolution. Too many insects have vision that is geared to seeing the special colours that they need to see. Bees have very complex relationships with plants and they have very complex vision to see the colours that plants exhibit to the bees that they rely on for pollination/fertilization. That is a whole field of study in itself.

[LPC]

Tobi, I seem to remember your posting a long time ago (maybe on the old forum?) about the fact that dogs can see colours that we can't - was it infra red, or ultra violet, or something else...? Maybe you can remember.

[Tobi]

This was the thread, LPC.:
http://www.animalloverswebforum.com/show...p?tid=2358

They are supposed to see better towards the ultra-violet end of the spectrum. Which means the red/orange, yellow end isn't seen as well, or at least not in the same colours as we see.
But of course, how do we know that for sure? We live and learn with most things, and many things we thought were so years ago, we have come to realise are not so.

[Catherine]

I had forgotten about that post. You did it while I was in Edmonton because I mentioned the dog sleeping with me. I don't get too many chances to sleep with a dog.

Dogs see more at the ultra violet end of the spectrum. I wonder now what the significance of that is. Why would ultra violet sight help dogs survive? Things develop because they help us survive. 

I think the world dogs see must be more vibrant than the one we see. They must get some important clues about the environment from the UV end of the light spectrum. Certain things glow under UV light. Dogs would see those things. Maybe it helps them to track things. If they can see a trace because of the UV vision, then they can use their sense of smell to track it.

Reptiles see more in the infra red spectrum. Snakes sense heat and can judge the size of something by its heat signature. That would matter to them because so many of them are nocturnal. They also don't need to really need to see details. They just need to know size and location of things around them.