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Tom Turkey’s Terrific Vision

The views expressed are those of the author and are not necessarily those of Scientific American.


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Not since Bugs Bunny and Elmer Fudd has there ever been such a set of rivals as Tom Turkey and Hunter Bob. Hunter Bob just can’t seem to get a turkey today. He’s new to hunting and said he wanted to ‘bag his own bird’ this Thanksgiving. Tom, on the other hand, isn’t about to let that happen.

Hunter Bob lays low in the bushes but he isn’t fooling Tom. So what gives Tom Turkey an advantage over his rifle wielding foe Bob? How about his superior vision?

Turkeys have incredible vision and are able to detect motion many, many yards away. Supposedly, they are even able to see up to 3 times greater than 20/20, though I can’t confirm this, I have never given a turkey an eye exam.

In addition to their excellent visual acuity, turkeys also have awesome peripheral vision. Tom’s laterally positioned eyes give him a broader field of view. He has an approximate visual field of 270 degrees around him, substantial compared to Bob’s measly 180 degrees. Put that together with Tom Turkey’s uncanny ability to rotate his neck completely around and he can spot the Bobs of the world coming a mile away, 360 degrees around him, with a simple twist of his head.

The fact that Tom’s eyes are spaced further from each other and are on the sides of his head does give him one small disadvantage; he lacks 3-D vision. Ok, Bob, you got him there. However, turkeys can compensate for their lack of binocularity by using a series of head bobbing movements, much like you may see pigeons do as they walk along the sidewalk in the park. These quick head movements allow their eyes to gather information about relative depths and distances of objects in their surroundings so they can do without true depth perception like Bob’s just fine. Sorry Bob.

Another aspect of Tom Turkey’s vision which is outstandingly terrific is his color vision and ability to see UVA light. Tom relies heavily on visual information to evade Bob and luckily he happens to be in a class of animals- birds- which have “the most complex retina of any vertebrae.”

The retinas of turkeys have seven different types of photoreceptors including 1 rod and 6 different types of cones, 2 of which are actually ‘double cones.’ Human retinas have only 4 different types of photoreceptors consisting of 1 rod and 3 single cones. One of Tom’s single cone photoreceptors has a spectral sensitivity to wavelengths near 400nm which is in the UVA light range. It is thought that being able to see UVA light helps birds when they are detecting prey, selecting a mate and foraging for food.

But what advantage (besides bragging rights) does seeing an extended part of the color spectrum give Tom over Bob? Well, you see, Bob is new to hunting and he bought a great new camouflage suit and vest for the occasion. Little did he know that the modern day laundry detergent he used to wash his new camo clothes in contained phosphates and other chemicals which whitened and brightened his clothes. These artificial brighteners also glow a bright blue color to turkeys who can see the ultraviolet light part of the color spectrum. So Bob, you may think you are doing a good job hiding in that natural looking roost you built using bushes and branches, but you might as well be a lost member of the Blue Man Group out here in the woods. It is hard for Tom not to notice someone wearing fluorescent blue clothes! Thanks to artificial brighteners, advantage once again goes to Tom.

Even if there is some way that Hunter Bob isn’t halted by Tom Turkey’s superior visual capabilities, Tom could most likely out run him. Turkeys can run about 20 mph. In contrast, the fastest human in the world has been clocked at running about 28 mph. Let’s say Bob happens to be very fast and is gaining on Tom. Well, Tom could always burst into flight and reach speeds of up to 55 mph. Can you fly, Bob? I think not. Tom Turkey once again proves to be elusive and does so this time with speed and style.

Bob, now don’t get discouraged you gave it a good shot. Maybe you should try to just make friends with Tom. Bury the hatchet, literally.

Why, you could even head up to Watkins Glen and attend the Farm Sanctuary’s “Celebration for Turkeys” event. You could watch turkeys feast on their own thanksgiving dinner of stuffed squash, pumpkin pie and cranberries served to them on silver platters. Maybe even ‘adopt a turkey’ there.

I guess what I am trying to say is: Bob, just stick to golf.

Happy Thanksgiving, everyone!

Photo credits: (Turkey Eye Exam) created with permission using pictures from Cheryl Murphy and stock photo ‘turkey’ by Gargi Bhuyan/ stock xchng, (Wild Turkey) stock photo by Yousif Waleed/ stock xchng, (Sammi and Aya eating pie) by Jo-Anne McArthur of We Animals / used with permission from Farm Sanctuary, (Author) Erica Angiolillo/ Gotcha by Erica!

Special Thanks to the Farm Sanctuary, visit their website for more information on how to visit the farm and donate to their farm animal rescue programs.

References:

Dickson, James G. The Wild turkey: biology and management. Mechanicsburg, PA: Stackpole Books, 1992. Print.

Hart NS. The visual ecology of avian photoreceptors. Prog Retin Eye Res. 2001 Sep;20(5):675-703. PMID: 11470455

Hart NS, Partridge JC, Cuthill IC. Visual pigments, cone oil droplets, ocular media and predicted spectral sensitivity in the domestic turkey (Meleagris gallopavo). Vision Res. 1999 Oct;39(20):3321-8. PMID: 10615498

Keeping UV Brighteners Out of Hunting Clothes.” Great Ghillies & Graphics.com Weblog. Great Ghillies & Graphics.com Weblog, 7 April 2010. Web. 1 Nov 2011.

Leighton, AH. The Turkey Vulture’s Eyes. The Auk. 1928 Jul; 45(3): 352-55.

Wild Turkey Facts. National Wild Turkey Federation, 2010. Web. 1 Nov 2011.

Cheryl Murphy About the Author: Cheryl G. Murphy is an optometrist and freelance science writer living and working in New York State. She began writing about vision science on her blog,Science Hidden in Plain Sight, in 2008. Links to her previous contributions to Scientific American’s guest blog can be found here. Follow her on Facebook or Twitter. Follow on Twitter @murphyod.

The views expressed are those of the author and are not necessarily those of Scientific American.






Comments 2 Comments

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  1. 1. Bonnie Nordby 11:52 am 11/23/2011

    Wow, I don’t see in 3D either Tom Turkey. I have a lazy eye and tend only to see out of one eye at a time. I have what is called switching. Now I worried I was missing out on something because of this. But I have found a new adaptive advantage. I can use my switching as a zoom and magnification device. Just learning to hunt and peck at this stage. I have front yard chickens and wild turkeys live close by. I think more field observation is called for from the visual perspective. Old farmers trick works against flies in the coop. Take a regular clear plastic bag, fill it 3/4 way with water, add one shiny penny and hang it in the coop. It really works. Flies have those multiple lenses, so the reflection the water bag prism fries the flies vision I think. They will only fly low to the ground in the coop now. Thanks for the special Thanksgiving Turkey Treat. Bonnie Nordby.

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  2. 2. poihths 8:55 pm 11/28/2011

    Turkeys may have terrific vision, but that doesn’t always help. In Ohio alone, and in the first week of the 2011 season alone, hunters bagged 7,744 turkeys. (See http://outdoornews.com/ohio/news/article_bd415a9e-7010-11e0-bed1-001cc4c03286.html.) Turkeys see motion very well, but hunters who know how to hold still, and how to imitate the sounds of a very sexy female turkey, can still put their own delicious wild bird on the table instead of a farmed bird who can’t walk, can’t fly, and can’t even reproduce. They do so by the thousands every year.

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