Hunters spend a lot of time worrying about a whitetail’s nose, but what about its other senses?
Everything about a whitetail’s vision is uniquely adapted to help it detect and escape predators. Take, for example, where the eyes are positioned, on the sides of its head. A deer can see 310 degrees, compared to about 180 degrees for humans. When it comes to peripheral vision, deer have us beat.
Understanding deer vision and how it differs from ours requires a basic understanding of eye anatomy.
Eyes contain specialized nerves called cones and rods. Different photopigments (or photoreceptors) in cones give animals and humans color vision. Rods are responsible for vision in low light.
Humans have three types of photopigments that enable us to perceive short, moderate and long wavelengths of light corresponding to blue, green and red colors — trichromatic color vision.
Deer have only two photopigment types, or dichromatic color vision. Deer can perceive short-wavelength blue light and moderate-wavelength light that they see as something between red and green.
“The net effect is the color spectrum for deer is vastly different from ours,” said George Gallagher, professor of animal science at Berry College in Georgia. “Deer see green as shades of grays to yellow and reds as yellow tones. Blues are more intense for deer than they are for us.”
This means is that a deer’s color vision is similar to a human with red-green color blindness. But they do see color.
Unlike humans, deer lack an ultraviolet (UV) filter in their lens, making their eyes more susceptible to the sun’s damaging UV rays. The trade-off is that deer can see short-wavelength blue and UV light that humans can’t detect.
“Some people still refuse to wear blaze orange but wear blue jeans to their stand, which is the opposite of what you should do if you’re trying to go unnoticed by deer,” said University of Georgia wildlife biologist Dr. Karl Miller. “Deer pick up blue very well, particularly in the morning and evening, but they don’t see blaze orange all that well, unless it has a shiny finish that reflects a lot of light.”
Gallagher and Miller worked with wildlife biologist Dr. Gino D’Angelo and Brian Murphy, wildlife biologist and CEO of the Quality Deer Management Association, to map out deer vision and identify differences between their vision and ours.
The researchers estimate that deer have 20/100 vision, meaning the level of detail they see at 20 feet is what normal human vision can see at 100 feet.
The biologists also discovered that deer have a higher ratio of rods to cones than humans, and a pupil 10 times larger. These factors, and the lack of a UV filter, give deer far superior vision in low light. “Deer are more than 100 times more sensitive to dim light than we are,” said Dr. Jay Neitz, a vision scientist at the University of Washington.
Unlike in humans, the cones in a deer’s eye are distributed across the back of the eye on a horizontal plane. The lens in a deer’s eye also can’t adjust much to objects at varying distances. These factors give deer less visual clarity than humans. An object a deer is looking at straight on is equally as in focus as something out to the side.
“Deer don’t see in three dimension very well,” Murphy said. “That’s why a deer will bob its head from side to side — they’re trying to get the object to move or see a different angle by looking behind the subject.”
But what deer lack in visual clarity, they more than make up for with a tremendous ability to pick up movement. “Movement is the biggest thing a deer’s eyes are focused on,” added Miller. “Even when you think a deer isn’t looking at you, be careful of your movements, because deer have such great peripheral vision.”
Neitz also cautions hunters against underestimating a deer’s vision. “Their vision is very well adapted to what they have to do. Even the idea that they can’t see fine detail is overblown.”
So a deer’s vision is not superior or inferior to ours; it’s just different. They have less clarity of vision, but they don’t need to count the whiskers on a wolf to know it’s a threat.
The biggest mistake most hunters make while hunting is moving too much. Wearing blue clothing also can give you away, particularly early in the morning and late in the afternoon. It’s a good idea to wear camouflage to break up your outline and help you blend in to your surroundings, provided it doesn’t contain UV brighteners or dyes.
“Based on how a deer sees its world, camouflage patterns comprised of large, solid shapes break up the human outline better than patterns with a lot of fine detail,” explained D’Angelo. “But it’s more important to use a good backdrop.”
At one time or another, just about all of us have had to swallow our hearts after making what we thought was a muffled noise, but one that sent a deer high-tailing it out of our hunting area.
This happened to me last year in Michigan. It was mid-November, and I was hunting with my 12-year-old nephew to help him harvest his first buck. At dusk, a buck ambled out of the brush 80 yards in front of us. My nephew struggled to take the safety off, which made a metallic clink that the buck probably heard. It looked right at us and slipped back into the brush before my nephew could get a shot.
It’s these experiences that make hunters swear a deer’s hearing is far superior to our own.
Before covering how well deer hear and differences between their hearing and ours, it’s important to understand some basics about sound.
Sound is a form of energy made when air molecules vibrate and move in a pattern of waves. The pitch, or frequency, is measured in hertz and describes how fast the air molecules are vibrating. The faster the vibration, the higher the frequency. Low-frequency sounds, such as human speech, travel farther than high-frequency sounds, like an arrow hitting metal.
To find out how well whitetails hear, Miller and D’Angelo placed deer ranging from 6 months to 5 years old in a soundproof booth, attached electrodes to each animal’s head and measured brainwave activity in response to different sound frequencies.
“A whitetail’s hearing capabilities aren’t that different from ours,” said Miller. “Their greatest capability is in the same range as sounds we hear.”
Like us, deer hear moderate frequencies best, those between 4,000 and 8,000 hertz. Deer vocalizations such as bawls, bleats and grunts are in this range. Deer can also detect sound at lower volumes than we can, although the difference is negligible. The upper end of human hearing is about 20,000 hertz, but whitetails can hear frequencies to at least 30,000 hertz.
Deer ears are uniquely shaped to pinpoint the source of sound much better than humans, too. Without turning its head, a whitetail can rotate its ears to pinpoint the source of a sound.
Whitetails are wired to determine quickly which sounds represent a threat and which ones don’t. This explains why deer run away after hearing two hunters whisper but stay put when hearing two squirrels playing. Whitetails are in the woods 24/7 — they know what does and doesn’t belong.
Hunters are the biggest source of foreign sounds. Bass Pro Shops hunter Bob Foulkrod refers to these sounds as noise pollution.
“A lot of hunters slam their door after getting out of their vehicle, talk to their buddy and then try to creep into the woods,” said Foulkrod. “Deer learn to attribute these sounds to humans, meaning a hunter reduces his chances of being successful before he gets near his treestand.”
Any unusual sound can trip a deer’s internal alarm. The cadence of human footfalls is another example. No four-legged animal sounds like a hunter walking. I know some hunters who mimic a deer walking by mixing up their walking cadence. Others occasionally use a turkey call while going to and from their blinds, but that only works if turkeys live in the area.
As with vision, a deer’s hearing is designed to help it detect what doesn’t belong. All hunters should respect a deer’s eyes and ears, but don’t go overboard. Slow down, minimize your movement and the amount of sound you make and do your best to blend in to your environment. It can mean the difference between harvesting a monster buck and just seeing the white of its tail. Read Recent Articles:
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• Hunting Below the Threshold: You can’t stop 100% of human scent, but you can reduce it to a huntable level.
This article was published in the September 2009 edition of Buckmasters Whitetail Magazine. Join today to have Buckmasters delivered to your home.