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Nimis's avatar

Do nocturnal animals have better peripheral vision during the daytime?

Asked by Nimis (13219points) May 17th, 2012

I’ve noticed that my peripheral vision at night is a lot better than my foveal (central) vision. I’m guessing that’s a throwback to the days when we had to sleep with one eye open for predators.

So that got me wondering if the reverse also held true.

Do animals that sleep (and are the most vulnerable) during the daytime have better peripheral vision during the daytime?

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3 Answers

thorninmud's avatar

In humans, the fovia is densely blanketed with cone cells, the photoreceptors that provided color vision and have the highest resolution. Away from the fovia the cone cells become sparse and rod cells predominate. The rods have low resolution and don’t handle color, but they function much better than cones in low-light conditions.

So at night, our fovia becomes almost useless, because the cells there can’t function in low light. The outer zones of the retina perform much better, so our peripheral vision predominates.

Nocturnal animals have a whole lot more rods than cones, but their central retina (many don’t have a fovia, properly speaking) is still more densely packed with rods than the periphery. A cat—which is naturally a nocturnal animal—has about 463,000 rods/mm^2 in the central area, and 250,000/mm^2 on the periphery. So even in the daytime, the cat’s central vision will be more acute than its peripheral vision.

Lightlyseared's avatar

No. The phenomenan you have noted it is due to the layout of the phohtoreceptor cells in the eye. The cells that detect detail and colour (cone cells) are concentrated at the centre of your retina and require strong light to trigger them. The rest of the retina is made up rod cells that require less light but only work in black and white. This is why you have better peripheral vision at night as your brain can concentrate on the info from the rod cells that cover a larger area of your retina – during the day the light is so bright that these cells are overloaded and so don’t provide useful info for the brain.

Your example of a nocturnal animal having better peripheral vision during the day supposes that the layout of rod and cone cells is reversed in the nocturnal eye but this is not the case. Infact a lot of nocturnal animals (bats for example) have no cone cells what so ever while most of have a massively reduced number of cones and significantly more rods.

Nimis's avatar

Sometimes just a few answers can be much more satisfying than a lot of responses.

Thanks, guys!
Good stuff.

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