The eyes of a whitetail: new research into the visual acuity of whitetails could help tip the odds in your favor this season!
Amazingly, he stopped broadside in a shooting lane and began to look around. With four eyes scanning the area, I had to wait until they were both looking away before I could make my move. Suddenly everything was right. I slowly took my bow off the hanger and moved carefully into position for a shot.
The sharp, blowing snort caught me completely off guard. Instinctively I turned my head back to the right to see a yearling buck, standing right where the doe had first appeared Moments before, eye-level with me His nose was pointed right at me and he was on full alert. He stomped his foot as he blew one more time. The doe bolted; the buck snuck away and I was left with, the little forkhorn in a face-off. I plopped back in my seat and let the waves of disappointment wash over me, In bowhunting, the highs are so high because the lows are so low.
Why are whitetails so good at picking off the slightest movement? You don't have to hunt very long before you experience the heartbreak of being busted by a deer that sees something out of place. We see a lot written about being busted by a deer that catches your scent, but how often do you get picked off by a little movement at the wrong time? Is there anything we can do about it?
Some recent research into deer vision reveals some remarkable things about how and what they see. Let's examine it and then see if we can mine anything that will make us more effective in the field. But first, let's lay the groundwork with a basic understanding of how the whitetail's eye works.
THE EYE AND HOW IT WORKS
Some research done recently at the University of Washington and the University of Georgia reveals some remarkable things about deer vision. Researchers dissected the eyes of deer and looked at them through high-powered microscopes. This revealed some very interesting findings about the differences between the eyes of predators and prey.
Eyes of all mammals are similar in structure, but there are significant differences in how they use them, and each mammal has various subtleties that help them survive in their environmental niche The eye of a deer is quite a bit larger in comparison to body size than many animals Their position does not allow for much movement, which is one characteristic that differs from human eyes.
The eye is made up of five basic parts contained within the ciliary body: the cornea, the lens, the retina, the pupil and the optic nerve head. The cornea is the protective layer over the lens and it is perfectly clear in deer, while in humans it has a UV filter. The lens is right behind the cornea and it serves to collect the light and direct it onto the retina. The pupil opens and closes to change the amount of light that passes into the eye. The retina is the back of the eye and the light that hits it is sent to the brain through the optic nerve. The retina in a deer is different in several ways, some of which give them significant advantages over predators. We will get deeper into that shortly.
So here is how the eye works in a nutshell: The retina is like a movie screen with light being cast upon it. Light comes through the lens, and is monitored by the opening and closing of the pupil. It is focused by the lens.
PREDATOR VS. PREY
Now here is where things get really interesting. The eyes of predators, like you and me, are optimized in a different way than those of prey species like deer. If you pay attention, you will notice that your eyes are moving along the lines of type as you read this. Your eyes have a very small point of focus, and everything within your field of view around that point of focus is peripheral vision, but it is out of focus. Look at something in the distance, and bounce your eyes around to look at different things around you. Your eyes move and settle on objects and then your eyes focus on that object. It's actually a small point that is in focus. That's because there is a small area on your retina (that screen in the back of the eye) that interprets the light coming through the lens.
The retinas of a deer actually have a wide band of area that can interpret light. Scientists call this a "visual streak." It's not very tall from top to bottom, but it is quite wide. Think of it this way: When a deer is looking straight ahead, almost the entire horizon is in focus at once! They do not have to bounce their eyes around like you and me. They do not even have to move their eyes at all. In fact, the deer's eyes are almost fixed in place and can move very little.
The eyes of a predator are positioned more towards the front of the head, while prey species have them more to the side. It takes two eyes at once (binocular vision) to correctly read depth perception. The brain calculates the difference in distances between the object and each eye, and provides an ability to see in three dimensions. We have binocular vision for our 120-degree field of view.
With the head stationary, a deer can see a 300-degree band around, him. And it is all in focus! A slight turn of the head either way reveals the other 60 degrees!
But there are some trade-offs. The visual acuity of the whitetail is surprisingly poor. In fact, they have about 20/40 vision. Plus, deer only have depth perception for that 60-degree area where their vision from both eyes overlaps in the front of them. If they really want to get a good look at something they must turn their head to see it well. While they may be terrific at picking up your movement anywhere around them, they can't really focus on you in three dimensions unless their nose is pointed at you so they can see you with both eyes.
Have you ever had a deer pick you off from across a field? They stand there and stare you down, sometimes take a few steps towards you or stomp a foot to get you to move. Remember, they have poor visual acuity and they simply can't figure out what they are seeing. Anything across a field is too far away to see clearly. If you have corrective lenses, then you know what I am talking about.
RODS AND CONES
How can you get away with wearing a bright "hunter orange" coat? Are deer able to see that color? There has been a lot of debate through the years about the color vision of whitetails. Because of this latest scientific research, that debate can now be settled. It was once thought that deer are "colorblind" and can only see in black and white and shades of gray. We now know that is not true. Deer actually see some colors better than we do, and some colors they can barely detect.
Without getting too technical, we need a basic understanding of the cellular structure of the retina. The two primary photoreceptors on the retina are rods and cones. Generally, cones are responsible for interpreting color, and rods are responsible for collecting light, which helps with low-light and night vision.
It's no surprise that deer have a much higher density of rods than we do. It's one of several reasons they can see at night so much better than we can. Plus, rods help detect motion.
Certain kinds of cones collect certain colors of light. Deer do not see the longer wavelengths as well and may not see much red at all. Orange is near the red end of the spectrum, so they do not see it well. Yet they see the short wavelength colors very well. They see blues better than we do. The yellows are somewhere in the middle. Additionally, human eyes have UV filters, and deer's eyes do not. Imagine a hunter wearing a blaze orange jacket and blue jeans. The blue jeans are going to jump right out at the deer and the orange is going to be a subdued color.
NIGHT TIME IS THE RIGHT TIME
One of the most fascinating aspects of learning more about deer vision is understanding why they see so well in low-light conditions. The reason deer see so well with so little light is found in three parts. I mentioned that they have a high density of rods in their eyes. Another component is that their pupil is a horizontal slit, which allows it to open very wide and cast a lot of light onto the lens. Compare that to your eyes, which have a round pupil that can open and close a small amount. This fact is responsible for the proverbial deer-in-the-headlights look. Because there is so much movement in the pupil, it takes them a long time to close it down when they see a bright light. This is one of the factors that has caused a lot of skid marks on the highways.
But the third component to this is even more interesting. On the back of the deer's eye, across the retina is a reflective substance called tapetum lucidum. When you see a deer's eye reflecting back at you from a light source, you are actually seeing the reflection of this shiny substance on the back of the eye. When light enters the eye, it passes over the lens and hits the retina. Because of the reflective tapetum, the light then bounces back to the front of the eye and reflects back to the retina again. This effectively doubles the amount of light that the eye can send to the brain for interpretation. All told, the combination of a wide pupil, the density of rods and the tapetum lucidum, makes for some very good night vision. One of the scientists who did some of the research, Dr. Jay Neitz, estimates that a white-tailed deer's eye can take in about 50 times as much light as a human's eye!
WHAT'S IN IT FOR ME?
So how can we use this new information to help us become better hunters? Any time we better understand our prey we have a better chance of making the most of an encounter. However, we can also pick a few gems out of this that can add to our success rates.
First of all, the knowledge that deer cannot see you well unless you are moving is not all that groundbreaking, but now we know why. That alone adds to the importance of keeping it in the front of your mind. We also know why it is so hard for deer to see us in a tree stand--because they have a band of focus and we are above that band. Yet they can pick out the slightest movement because they have such a wide field of view. Think about that the next time you reach into your pack for a granola bar or turn the page on the book you are reading during that long sit on stand. Slow, deliberate movements are a must.
Remember that the lower the light, the bigger advantage the deer has. After learning this information, I have determined to get out of my tree stand a little earlier and sneak out while I can still see without a flash-light. Mature bucks, once spooked, might never return to that spot again. I would rather give up 10 minutes of shooting than risk busting a buck.
Just because you can't see both of a deer's eyes doesn't mean he can't see you. Choose your timing carefully and make your move when you have the best chance of being undetected.
We now know more than ever before about how and what deer see. Some of this information confirms our suspicions, and some of it gives us new ammo. It will be interesting to see how this newfound knowledge changes the way we hunt.
RELATED ARTICLE: MAXIMIZE YOUR ADVANTAGE
There are four new camouflage patterns that attempt to improve hunter concealment by taking advantage of the differences in deer vision compared to human vision.
Gore's Optifade camouflage is a radical departure from what camo patterns have been trying to accomplish. Gore actually hired whitetail vision scientist Dr. jay Neitz to help them develop the pattern. While most camo patterns are attempting to mimic the environment, Optifade attempts to use the science of what deer see to create a pattern that would prevent the animal from recognizing the hunter as a predator. They also used the services of Col. Tim O'Neil and Guy Cramer, experts in the field of digital concealment. Just like the U.S. military has used digital camo patterns that make it hard for people to see, Gore has used digital patterns based on the science of ungulate vision that makes it hard for deer to see. The micro-pattern takes into account the way deer perceive color, the ratio of positive to negative space and other visual elements. This allows the hunter simply to blend in without having the realistic elements of the habitat on the pattern. If simply breaks up the symmetry of the body shape. The Big Game/Forest pattern also takes into account the angles found while treestand hunting. (www.optifade.com)
Scent-Lok's Vertigo was developed by using a mannequin and taping patterns to it with the belief that if there were large areas of contrast, it would make it hard for the deer to pick it out against a combination of sky and branches. While it is specifically designed for tree stand hunting, Mike Andrews of Scent-Lok says he has been surprised at how well it works on the ground. While most camos are designed simply to break up the outline with a more or less random mass of branches, leaves and colors, Andrews says this one is laid out with the person's figure in mind on each article of clothing. (www.scentlok.com)
Realtree's All Purpose High Definition (HD) takes the concept of focus to a new level, with high-resolution prints in their HD pattern. Realtree's Dodd Clifton says that there are 12-14 colors in each of the AP patterns, and Realtree has developed a new high-definition process of printing. He feels they have used the best combinations of tones and elements for a camo pattern that works in a variety of habitats. The camo has a three-dimensional look because some of the elements are in sharp focus and some are out of focus, giving the illusion of depth. (www.realtree.com)
Mossy Oak's Break-up Infinity also uses various focus elements to create the illusion of depth. "It's like you are looking right into the woods," says Mossy Oak's Joedee Robinson. It is an evolution of the popular Break-up pattern but if has lighter tones and more areas of contrast. The elements are based on real photos and the pattern offers lighter tones to the elements in the parts that appear to be in the foreground, and darker tones to the elements that would be in the shady background. (www.mossvoak.com) --By Bernie Barringer
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|Publication:||North American Whitetail|
|Date:||Oct 1, 2010|
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