Can anyone tell me why house cats have a diamond shaped iris?

I asked this before but my subconcious will not allow the answers I received. I was told cats iris are shaped like this because they hunt at night. However, large cats do not display this. They have a round shaped iris--lion/tiger/leopard/ etc...I also have noted a large amount of other nocturnal creatures who do not share this physical trait. The next creatures I have thought of would be the lizard family as they have this diamond shape of an iris. But lizards are day creatures because they are cold blooded and require day light to aid their metabolism.





So then where does this biological difference originate. If house cats and lions are related where on the tree of life did this difference come from.

Can anyone tell me why house cats have a diamond shaped iris?
House cats have wide round iris which, when narrowing, become oval. That's a way to focus which can be found in other wild cats (the small felines, not the big ones like lions and tigers) except for the Manul cat. Cats are nocturnal hunters mostly, narrowing their iris to a slit is a way to better protect their light sensitive eyes.


Goats have a horizontal rectangular iris all the time.


Humans become just smaller round balls.
Reply:The iris changes shape depending on the light conditions. In low light and at night it creates a wide open round pupil to allow as much light in as possible. My guess is that during the day most cats are sleepers and the large pupil is not needed, so they have evolved an eye that minimizes the capture of light by creating slit like or thin diamond shaped pupils, but which will react to low light conditions at night and prime the animal for nocturnal hunting.
Reply:Although a round pupil allows an optical system to produce somewhat better image quality, irises that closes to a slit like those of housecats and horses can be controlled by a lot simpler system of muscles and ligaments.
Reply:Sorry Homy1canoby,i realy dont know.I haven't even noticed that cats have a dimond shaped iris.

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