|MadSci Network: Zoology|
Lane, Thanks for your question. The first thing I would like to point out is that it is a mistake to assume that animals either have colour vision or they do not. There is a broad range of degrees of colour vision, and even animals which seem to be able to recognise the same colours we do, are unlikely to see the world in the same way. Even within our own species, you know that many people are colour-blind to varying degrees, with minimal effect on their everyday lives. There are two types of light-receptors in mammalian eyes. "Rods" which detect only levels of light, and movement, in monochrome, and "cones" which can distinguish colours. Rods are much more sensitive, especially at low light levels, and are thinner, so that more can be packed into a small area, giving greater visual acuity. It therefore makes sense for "prey" animals like deer to have mostly rods, so that they are sensitive to movement and see more clearly at night, when they are most active. Studies of deer eyes have shown that they do in fact have some cones, but nowhere near as many as we do, so they probably do have some colour vision, but perhaps something like a "colour-blind" human, and only in bright light. It is interesting to note that some hunters in the US are now wearing orange caps or jackets to prevent themselves being shot by their friends, but with no apparent effect on their visibility to their prey. PS Don't feel sorry for the deer - my colourblind friend tells me that he sees many more subtle shades than me, and think he has the better deal !
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