Years ago one of my graduate students was taking imprinted wild turkeys into the field to see what they ate.
Often I’d tag along. Several times I noticed that the poults (about 10 weeks of age) would stop and look into the sky then seek cover. At first I thought they were spotting hawks in the air, but I never saw one. Then one day I realized they were seeing jet planes 30,000 feet up. Amazing.
It turns out that turkeys have very good vision and detect movements really well.
Their eyes are at the side of their head and each eye is constantly on the lookout for predators.
They literally can see almost 360 degrees. Our eyes are forward, and our range of vision is only 180 degrees. We don’t have “eyes in back of our heads”, as the saying goes.
Even when we turn our necks as far as we can, there is a considerable blind area behind us that can only be seen if we twist our whole body around. Not so with turkeys.
Turkeys need that advantage because ground predators are always around. One Achilles heal for turkeys is their poor night vision. That is probably why turkeys roost in trees at night. They do so to avoid predators.
Years ago I was bowhunting in Montana and just before dark I watched a large flock of turkeys fly up into a big nearby tree.
There was a full moon so I had some vision as I descended from my tree stand and started walking to my car. That walk took me right past the tree where the turkeys were located and I could see them against the sky.
As I stopped and watched, a great-horned owl swooped in and nailed one of those birds and it flew to the ground carrying that turkey. I couldn’t see them, but could hear the noise as the owl killed that turkey and started eating it. How common is that? Probably not very common, but it happens and it was amazing to witness.
How about deer vision? Deer have their eyes at the side of their heads, though not as prominently as turkeys.
As with humans they have binocular vision where what they see with one eye overlaps with what they see with the other. Our binocular vision is 120 degrees. A deer’s is only 60 degrees. And the field of view for us is 180 degrees as I mentioned before, but that of a deer is 310 degrees. Deer have a dead spot behind them unless they turn their body.
A deer can see around them (310 degrees without moving their head, but since a deer only has binocular vision of 60 degrees, if they are looking at something and it doesn’t move, they have trouble seeing it. But they can readily spot movement in those 60 degrees.
Hunters learn that quickly. If a hunter is out of the 60 degree line of sight, they can get away with slight movement and the deer won’t see them.
However, deer have other advantages that we don’t have. In low light they see well. At night they see well. If they didn’t, they’d be crashing into trees, etc. at night.
There are several advantages deer have. First, their pupil is slot shaped and is parallel to the ground. That means they can receive more light in front and less from above and below. That also means they can see predators at ground level much better.
Deer also has a tapetum in the back of their eye that is like a mirror. It reflects light that enters the eye back to receptor cells.
Light hits those cells when it first enters the eye, then again when the tapetum reflects it back again. The tapetum is why you can see a deer’s eyes when a light from your car headlight hits them. That’s the light being reflected back from the tapetum.
When it comes to predation, for deer and turkeys, the eyes are the key. That’s especially true for the position of the eyes.
Dr. Dave Samuel is a retired wildlife professor from West Virginia University. His outdoor columns have appeared, and continue to appear, in Bowhunter magazine and the Whitetail Journal. If you have questions or comments on wildlife and conservation issues, email him at drdave4@comcast.net.
