The eyes other other mammals have some type of pupil that can dilate to let more light in. However, the eyes of rats and mice just seem to just have a large black pupil that doesn’t dilate or contract. Why is that?
In: Biology
They do actually have a pupil it’s just that usually you’ll only see it if you happen to see their eyes in the right light at just the right angle [this gives an example](https://howling-techie.tumblr.com/post/626462178223996928/ratichu-something-i-love-about-rats-is-their)
Most Rats & Mice have Black eyes which is why they look like they don’t have irises. There are pink eyed ones which are albinos & Ones with Ruby eyes, they look black until they are in bright light then their eyes are dark red, this is caused by a similar gene mutation like the Lutino one in birds, all birds with the Lutino gene mutation have bright yellow feathers & Ruby Red Eyes regardless of breed.
Mostly they just have big dark irises that cover most of the visible eyeball around the pupil.
Actually if you look at most mammals you will find that this is the case, it’s just a bit easier to see the iris as distinct from the pupil in animals with larger eyes. Actually showing the white part of the eye is unusual in nonhuman mammals.
So why do humans do it? Well, humans are very social and often cooperate on complex tasks in a way that other mammals don’t. It’s thought that by showing the whites of our eyes we make it easier to track each other’s vison, which makes coordinating action easier since it’s easier to tell what the other person is looking at.
Latest Answers