Researchers know quite a lot about the eyesight and hearing of whitetail deer. A deer’s sense of smell may be more mysterious to scientists, but one thing is clear to experts and most hunters alike: It’s a deer’s most powerful asset.
Biology of a Deer’s Sense of Smell
Deer survive by their nose, says wildlife biologist Kip Adams. It’s the primary tool they use to avoid predators and find food. They also use scent to communicate with other deer far more often than we humans might realize.
“Scent is by far the most heightened sense that they have,” says Adams, who is also the chief conservation officer for the National Deer Association. “Their nose is what they use, literally, to find food and not get killed each day. Hence the reason that their sense of smell is so much better than their eyesight, so much better than their hearing. Scent is everything for a deer.”
That’s one reason why whitetail deer probably evolved such an elongated face: to accommodate all the nasal tissue that contains olfactory receptors. (An olfactory receptor is simply a protein that detects odors, and makes up a mammal’s sense of smell.)
“People look at that black spot on the end of a deer’s face as their nose,” says Adams. “But the deer’s nose really runs from the tip all the way up through the head into the brain. That nasal canal is full of olfactory receptor cells. And they curve back and forth to increase the surface area, and allow more of them in that space.”
Related: How Long Do Whitetail Deer Live?
No one is really sure how many olfactory receptors whitetails have. One oft-cited stat from the early 90s estimated deer had nearly 300 million olfactory receptors, but experts now think that’s lower than reality. Some research shows dogs have between 125 and 300 million olfactory receptors, and that depends on the breed. Flatter-faced dogs have fewer, while long-snouted breeds like bloodhounds (known for their scent work) have about 300 million ORs. By comparison, humans have somewhere between 5 and 50 million depending which study you look at.
“We don’t know how many times better whitetails can smell than humans, but we do know that they have about 100,000 times more sensory olfactory receptor cells than we do,” says Adams. “Now does that mean they can smell 100,000 times better? We don’t know, but probably it’s at least on that order of magnitude better.”
Biologists estimate that mule deer, as a species, are about 50,000 years old. That sounds pretty ancient until you hear that whitetail deer are about 4 million years old. They are the oldest deer species, says Adams, and that’s important for modern deer hunters to remember.
“That’s a long time to really refine everything,” says Adams. “Deer are so good at what they do.”
What Hunters Need to Know About a Deer’s Nose
There’s no research that suggests scent-eliminator sprays and devices like Ozonics, which produce odor-neutralizing ozone particles, can completely fool a deer’s nose. Studies do show some mixed results, like one analysis out of Mississippi State University that found scent reducing sprays eliminated some, though not all, of the many volatile compounds human bodies produce that are associated with odors. There are also plenty of anecdotal hunter accounts that swear by both.
“There is nothing that can make us invisible to deer from a scent standpoint,” says Adams. “Even if we could become invisible [to a deer’s nose] when we left the house, we are giving off additional scent with every breath we take. There are hunters who think they are entirely invisible from a scent-perspective, and I think they are being a little naive.”
Related: 15 Scent Control Strategies That Actually Work for Deer Hunting
Still, Adams practices what he would call moderate scent control, and he thinks “it’s absolutely advantageous to hunters to work on scent control.” For him, that means laundering his camo in scent-free detergent, storing it in plastic bins, and dressing for a hunt right before he leaves the house and stowing his camo promptly upon his return.
Practicing some scent control in the deer woods can’t hurt, and he doesn’t see any harm in going full-out with militant scent control — if that’s something that brings you more confidence in the woods.
“I’m not fooling myself into thinking deer totally can’t smell me, but I think it does help reduce the amount of scent that I carry into the woods with me,” says Adams, who is an experienced Pennsylvania deer hunter.
But scent control is no replacement for common-sense hunting strategies that factor in a deer’s sense of smell. To avoid getting busted while hunting, the best thing you can do is still choose stand locations that consider the direction of the wind, the likely direction of deer travel, and thermals. You must also pay careful attention to your access routes to each stand stand site, as deer can easily pick up ground scent from your boot tracks.
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Adams finds that the average hunter today definitely pays attention to the wind. Still, he’s surprised how often he ends up in a deer camp with folks who don’t give a deer’s nose a second thought when planning their hunts.
“There’s still a bunch of people today who pay almost no attention to the wind when selecting stand sites or areas for habitat work,” Adams says. “So pay attention to that and make sure wind and thermals are not blowing your scent to where you think deer are coming from. That alone can make a big difference in how many deer you see. It’s a little elementary, but I’ve been surprised at the looks I get when I start giving a seminar to certain hunting groups … it’s like I’m talking calculus to them.”
Hunting Pressure and Deer Smell
There are several studies that have been done that show hunter pressure causes deer to clear out of an area, and one study out of Auburn University demonstrated that bucks took an average of three days to return to a stand site that had been hunted.
Those studies have not isolated which part of a human’s presence is responsible for driving deer away. But if Adams had to make an educated guess, he suspects scent plays a big role.
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“It’s pretty clear that once human pressure has been in an area, deer avoid those areas,” says Adams. “That doesn’t necessarily mean they had to see somebody, it’s just they knew [a human] was there. Just because scent is so much more important to deer, I have to think that scent is a component of pressure.”
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