Why do dog’s or cat’s eyes flash blue when a photo is taken?
In: Biology
There is a reflective layer behind the retina that reflects back light, it gives the light a second chance of getting absorbed by the photoreceptors. This results in better night vision with the drawback of a slight bluring of the vision, the light will not get reflected straight back from where it came.
It might seem like a huge disadvantage because it make them easier to spot. What you then forget is you need a light source that emits light that gets reflected back, It needs to be close to the observer because the light is mostly reflected from where it came. Only humans has light sources like that and we have got effective light sources quite recently. So reflecting light has not been an evolutionary disadvantage.
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