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Question:
Why do snowy owls have YELLOW eyes??


Replies:
I don't have a good answer for you, but can tell you that I own a number of authoritative books on owls and none of them answered this question (which I was asked during a presentation). I did find an interesting rule of thumb that says strictly nocturnal owls have dark eyes and owls with yellow eyes are sometimes active during the day, but it's not always clear cut (Barn Owl perhaps being the best violation of the rule). But this doesn't tell us much about the "why".

Many animals have very colorful eyes (and other body parts). A common explanation for pigments is "sexual selection", meaning that animals tend to choose traits that indicate a healthy mate. Pigments such as melanin and carotenoids require protein in the diet for the body to manufacture them and thus these colors may be an indicator of an animals ability to find and metabolize nutritive food. So it could be that yellow eyes are a general indicator of reproductive fitness. My guess is that because owls have essentially no color vision at night, the strictly nocturnal owls have no use for colorful eyes, but this is strictly a guess.

In humans, there is evidence that dark eyes are protective against some degenerative eye diseases. Furthermore, eye and skin color share some genes, so as skin tones generally are lighter at less sunny latitudes, the eyes also tend to get lighter. So you can see there may be a number of subtle and complex reasons, for humans as well as owls.

Paul B.


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