Making Sense Of A Whitetail Deer’s Defense System

Sitting in the fall deer woods, one’s mind has a tendency to wander, including questions about the honey-do lists; which fish are biting today; are the mallards flying; or whatever else creeps into your mind. For many of us, we try to add to the book that we all have filed away in our minds. Each chapter in each individual’s book is filled with different facts. For those of us who spend so much time in the woods, we try to figure out the critters we chase.

For deer hunters, there are three main things we best beat/disguise/blend into to fill our tags each time we step into the woods. The whitetail deer has three main defenses that are all but difficult to beat – their eyes, their nose and their big ears.

Understanding the big three is the first step/chapter in the book. Let’s take a look at each of the whitetail deer senses and maybe offer a couple suggestions on how to get over on them.

The huge nose on a deer face isn’t there for looks, but it’s used as what some would say their main line of defense. Some question that a deer’s sense of smell is their most important line of defense, but I would say that’s a discussion for a later date.

So, what makes a deer’s sense of smell so important? Let us consider the interior of a deer’s nose. It has hundreds of thousands, if not millions, of nerve cells. In fact, there are probably thousands of groups of cells in the nose, and each group can detect one odor. This means that a deer has a group of cells in its nose that can detect acorns, and others that detect alfalfa, corn, certain twigs, dead leaves and dogs. There are nerve cells dedicated to detecting other deer, human deodorant, gasoline on gloves, and so on and so on.

You name the odor, and a deer has a group of cells located in one tiny region of the nose that can smell that odor.

Once that odor hits those receptor cells, it triggers an area of the deer’s brain, including when a deer smells an acorn, that activates the acorn nerve cells in the nose and that then sends a message to a part of the brain which leads to a pattern of behavior. Therein lies the key to how deer get you. If a young deer has a bad experience with a dog, a pattern of behavior is created in that deer’s brain. The next time the deer smells a dog, the deer flees. But if this deer grows up in a park where there is no hunting, and people walk their dogs on a leash all the time, then a dog’s odor probably won’t trigger that same negative response.

Pursuing that idea further: if a deer grows up in an urban environment – a slow drive around downtown Jamestown will prove this point – then the odors it smells related to humans won’t trigger a negative response. But if that deer first smells a human odor in the wild and the initial encounter was negative, then the moment the deer gets a whiff of the same human odor again, it bolts.

There has been some research suggesting genetics are involved, essentially coding scent receptors to recognize certain smells

While we don’t know the number of olfaction genes a deer has, we do know the number of olfactory scent receptors. In a recent study, deer are reported to have 297 million scent receptors. In comparison, humans have five million and dogs have 220 million.

I have long believed that not only do deer have at least 2,000 percent more scent receptors than humans, buy they also have more different types of receptors. Meaning, deer can detect scents that humans simply can’t comprehend.

Here is the important part for hunters. How do we overcome a deer sense of smell. My belief is that it is simple as the wind. Always use the wind to your advantage. Set-up and hunt a deer downwind. If you are hunting deer trails or scrape lines or bedding areas, always set up so the wind doesn’t blow your odor to the deer.

It’s happened to every bowhunter. A deer spots you for no apparent reason while perfectly concealed. Was it your scent, your noise, your movement, or perhaps what you were wearing? While all hunters agree that deer have an amazing ability to detect movement, the consensus regarding what colors deer can see is far less unanimous. Because of this, many hunters, especially bowhunters, are concerned that wearing blaze orange reduces their chances of success.

Another topic of debate is camouflage clothing. During the past decade, there has been rapid growth in the number and variety of camouflage patterns available to hunters. This has occurred despite little knowledge of what game animals actually see.

A more recent question is whether deer can see ultraviolet light. UV light is the type of light that causes your clothes to “glow” when near insect zappers or nightclub lights. Many laundry products and dyes used in the manufacture and care of hunting clothing contain “color brighteners” or more technically, UV “enhancers.” This is why clothes containing these products look “brighter” and “whiter” to the human eye. It has been proposed that hunters wearing UV-treated clothes actually “glow” to deer.

Fortunately, many of these arguments can be laid to rest due to the results of several studies conducted since the early 1990s. Studies were done at the University of Georgia in 1992 on this very topic.

The study confirmed that deer possess two rather than three – as in humans – types of cone photopigments allowing limited color vision. The cone photopigment deer lack is the “red” cone, or the one sensitive to long wavelength colors such as red and orange. These colors aren’t invisible to deer, but rather are perceived differently. Deer are essentially red-green colorblind like some humans. Their color vision is limited to the short-blue and middle-green-wavelength colors. As a result, deer likely can distinguish blue from red, but not green from red, or orange from red. Therefore, it appears that hunters would be equally suited wearing green, red, or orange clothing but disadvantaged wearing blue.

Regarding UV they confirmed that, unlike humans, deer lack a UV filter in their eyes. In humans, this filter blocks about 99 percent of damaging UV light from entering the eye. It also functions much like a pair of yellow shooting glasses and allows us to focus more sharply on fine detail. The trade-off is a loss of sensitivity to short wavelength colors, especially in the UV spectrum. Because deer do not have a UV filter, they see much better in the UV spectrum but lack the ability to see fine detail. This helps explain why deer often move their head from side to side when they encounter a hunter.

Vision occurs when light enters the eye and is absorbed by specialized cells located in the back of the eye. These cells send a signal to the brain which is translated into sight. The color perceived by the brain is determined by the wavelength of light reflected. In other words, objects do not actually have color, they simply reflect light of a particular wavelength that our brain perceives as color. The spectrum of color ranges from ultraviolet on the short end of the spectrum to infrared on the long end. Humans can see the range of colors between, but not including, these two extremes.

Understanding the general makeup of the eye also is important. In all mammals, the retina, located at the back of the eye, consists of two types of light sensitive cells called rods and cones. Rods function in the absence, or near absence, of light and allow only black and white vision. Cones function in full light and permit daytime and color vision. Humans can see a wide range of colors because we have three types of cone photopigments specialized photoreceptor cells in our eye. One is sensitive to short wavelength light-blue, one is sensitive to middle wavelength light-green and the third is sensitive to long wavelength light-red. This three-color, or trichromatic, vision is the most advanced form of color vision known in mammals.

As far as a deer’s senses are concerned, their daytime and color vision are pretty average. In fact, the actual color of the fabric is relatively unimportant as long as the pattern blends with your surroundings. Therefore, camouflage clothing is still recommended. In contrast, solid unbroken patterns, especially of light colors, are not recommended. Similarly, garments made from vinyl or plastic should be avoided because they reflect light much like the glare from a gun barrel.

Should hunters be concerned about the UV brightness of their clothes? Probably, since the 1992 study revealed that deer can see into the shorter wavelengths were UV light could be noticeable to deer. If concerned about the UV brightness of your hunting clothes, you should first determine if they are giving off UV rays/”UV-hot.” This can be done easily with the aid of a UV or blue light. If the clothes glow under the light, the UV radiance must be eliminated with a special product made for that purpose. If the clothes do not glow, simply avoid washing them in laundry products containing UV brighteners and you will be good to go. This is another example of how hunters can use the latest research to improve their hunting success.

Regarding a deer’s sense of hearing, those huge ears on the sides of a deer’s head play an important role in their daily survival. The older I get, the more important I feel hearing is. It’s been said that if I had to use my ears to survive, I wouldn’t last a day in the wild. Like my dad says, “welcome to old age, son.”

A recent study on deer hearing has shown that their hearing range extends from .25 kHz to 230 kHz, but is best at 28 kHz. The interesting part of the study is those frequencies differ very little from our hearing which is best between two and 5 kHz, with an upper range of 20 kHz.

Researchers noted that deer detect higher noise frequencies than humans, but pinpointing that high frequency range is where the major differences start to show up. A deer can pinpoint noise much better than the average human.

A few things can have an influence on a deer’s nose, including humidity, air temperature, vegetation, overhead foliage and which way their ears are pointed at a given time. Being able to hear 360 degrees is very important to a deer’s sense of hearing.

So, while a deer’s hearing is 100 times better than the average human, it’s their pinpointing the direction of the sound that is where the major difference comes into play. While a deer can hear a twig snap at quarter-mile away, it’s their ears, mind and body working together that helps them know where the sound came from, which generally follows with their famous goodbye wave – tail in the air.

Which of the senses are the most important? I’m not really sure, and those with much more knowledge aren’t sure either, so who am I to say? What I do know is this: to get a deer in range for a clean bow shot one needs to be quiet, stay up wind and don’t move/blend in. While these are all great and widely known, the key is to put them all together and make a good shot.

Best of luck this stick and string season and remember coming home safe is more important than venison.


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