Posts Tagged ‘pupil’

by , Keeper
I've been at the museum since 2010. I love to read and learn; it's rare that a day goes by at work when I'm not suppressing the urge to spew out something cool I just learned to my coworkers. In my spare time, I play the 'cello, snuggle my dog and reminisce about snowmen and Nor'easters.
I work Sunday through Thursday. You can find me raking the Farmyard in the morning or training the donkey and dwarf goats in the afternoon.

I Spy

September 9th, 2012

Have you ever looked closely at a goat or sheep and noticed their weird rectangular eyes? I hear guests commenting on them every few weeks; some people love them, some people are disturbed by them, I think they’re awesome!

Sheep goat eyes

Mutton Sheep, Rocky Goat, and Chummix Goat.

Ungulates (hooved animals) are prey animals and need to have a great field of vision to avoid being snuck up on by a predator while they’re grazing. The rectangular pupil of the sheep and goats allow them to see in nearly a full circle around them: 320-340 degrees! This has some disadvantages, though. The flattened pupil disallows goats and sheep to look upwards or downwards without raising or lowering their heads. This is why, if you reach out to pet a goat’s head, they’ll often step back and look up at your hand. They can’t see you when you’re directly above them.

optifade

© 2011 W. L. Gore & Associates, Inc.
Human versus Ungulate Field of Vision

Equine, cattle and pigs have large eyes with round pupils on the sides of their heads, which gives them around 300 degrees of vision but they can see a little better above and below their eye level than goats and sheep can. They still need to raise or lower their heads to gauge distance above and below eye level because depth perception exists only where the vision from both eyes cross. With one eye on each side of the head, the area in front of the animal where the vision crosses (called binocular vision) is fairly small: 20-60 degrees for sheep and goats, and 60 degrees for equine, cattle and pigs. These animals also have blind spots directly in front of their face and directly behind their back legs. This is why walking behind a horse or steer could get you hurt. They can hear you back there, but not see you. The animal may kick to protect itself.

Donkey and Steer

Lightning the Donkey and Max the Steer.

Predators don’t need to see all the way around their bodies as much as they need to be able to gauge distance in front of them. Humans and bears have eyes with round pupils on the front of their heads so that more of the vision from each eye overlaps and there’s a larger area of depth perception. Humans can see about 120 degrees around themselves but have 100 degrees of binocular vision.

bear human

Virginia bear and a human eye

Check out these other cool animal department eyes! Do you know to whom they belong?

more eyes

 

 

Join the conversation:

  1. Great Post!

    Posted by kimberly
  2. Keeper Comment :

    It’s a little late, but I’ve got to correct my post slightly.

    It turns out that cattle have rectangular pupils like sheep and goats! I thought they were round because Max’s eyes are so dark brown that the black pupil is virtually indistinguishable from the iris. However, the sunlight caught Max’s eye just right and sure enough, he also has a rectangular pupil like the sheep and goats!

    Posted by Sarah Van de Berg

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