I have been an avid bowhunter for the last 30 years. Currently I train dogs for law enforcement. The dogs are trained in narcotics detection, tracking and other methods to locate humans. These two areas of knowledge give me a unique understanding of how dogs and deer utilize their sense of smell. Dogs possess up to 220 million olfactory (scent) receptors and can detect some odors in parts per trillion. A dogs sense of smell is 10,000 - 100,000 times greater than ours. “let’s suppose they’re just 10,000 times better,” says James Walker, former director of the Sensory Research Institute at Florida State University, “If you make the analogy to vision, what you and I can see at a third of a mile, a dog could see more than 3,000 miles away and still see as well”. Conversely a deer has up to 297 million olfactory receptors compared to humans having only 5 million. Books on training dogs date back to the mid1800’s and our ability to observe dogs recognition and response to odor is invaluable as it relates to how a deer utilizes its sense of smell. That being said it is important to understand that deer and dogs approach odor recognition from completely opposite ends of the spectrum. Dogs are trained to located the lowest detectable amount of odor (absolute threshold). Dogs then are able to determine direction and follow the odor to its source by following the slightest change in odor concentration (just noticeable difference JND). Deer detect odor and then have to make a determination wether or not they are in danger. This decision is based on past experience and is the equivalent to a subconscious distance calculation based on the amount of odor detected.
The key element of the “scent control” discussion is recognizing that scent control is a tactic not a hunting philosophy. It is a tactic similar to the use of a grunt call. You don't need to use a grunt call but In some situations it may be beneficial. For the purpose of this discussion I will refer to “scent control” as measures to reduce human odor. This would include washing and maintaining clothing, sprays, oral use of chlorophyl and Scentlok clothing/activated carbon. The use of cover scents and ozone would fall in separate categories. The problem is that scent control constantly gets debated on wether or not it works. Of course it works. I think everyone recognizes that we can reduce human odor. The argument is that with deer having such an acute sense of smell attempts to do so are futile and a waste of time. The issue is further muddied when proponents of scent control allude to the goal of being “scent free”. This is where the scent control argument is completely lost. Hunters on the side of scent control and Scentlok have countless instances of “proof” that it works and the hunters who don’t use scent control have the guy who farts in his Scentlok bibs and a wall full of bucks to say it's a waste of time.
The fact is that deer smell all kinds of things and through life experience assign a level of danger to that odor. A deers sense of smell is its greatest sense and it uses it similar to how we rely on our eye site. Deer clearly show odor recognition by licking their nose and head movement as they determine direction of the odor by interpreting the slightest variance of odor concentration (JND). More importantly a deer uses its sense of smell not only to identify odors but to calculate distance to that odor. This can clearly be observed in tracking dogs as they clearly exhibited changes in behavior as they get closer to the source of the odor. I have no doubt that they can tell exactly how far away the source of the odor is. A certain amount of odor particles correlates to a certain distance. 24/7/365 days a year deer utilize their sense of smell to compute distance. Very few deer have never smelled a human so every deer has a distance it will tolerate in a variety of locations it travels. It is not that it doesn’t smell human odor it is that based on its past experience in that location it is not in danger or has a lower level of concern. This directly relates to hunting pressure and the tolerance of deer to human odor in an urban environment. Deer will have no problem with people moving around in their backyards but if those same people take one extra step into the woods it is a different story.
Scent control is not the act of having no human odor. It is more of an optical illusion. A human smells a certain way at a certain distance. This is based on the deers past experience with human odor related with its daily exposure to all different kinds of odor molecules. A certain level of odor concentration equals a distance. It is a subconscious calculation made by the deer. Similar to us passing a car on a divided highway. We use our sense of sight to make a complex mathematical calculation involving the closing speeds of three vehicles moving at different speeds over an unknown length of roadway. Think how fast we make this decision. Very few of us could actually do the calculation on a piece of paper but we do it all the time. Now imagine that I narrowed the approaching road and put a smaller car approaching in the opposite lane. All our previous calculations were based on what we believed the width of the roadway is and what the size of a car normally is. How much of an impact would that have on the accuracy of that calculation? This is the essence of scent control. If you can lower the amount of human odor you can represent to the deer that you are located further away than is actual. Scent control can give you that “one more step” that is so critical when it comes to bowhunting. It would also be important to say that hunting height has a huge impact on the deers ability to calculate distance and that height alone can reduce odor in a variety of situations.
Scent control is a simple cost vs benefit calculation. The cost of scent control is the effort and time it takes to maintain your clothing, equipment and personal hygiene. It also includes how all that work affects where you decide to hunt. Hard core scent control enthusiasts are far less likely to hike 3 miles to get to their stand because it would require a complete overhaul of their equipment following the hunt. Everything would need to be rewashed because it would be extremely difficult to control sweating with that type of physical exertion. Scent control as a tactic is not necessary or even practical when used in a variety of different hunting strategies. Gun hunters worry very little about scent control because they are normally located at a distance that is outside the area of concern for the deer. Western hunters have little interest in scent control because it is impractical when combined with walking up and down mountain ridges. You would be unable to maintain the clothing or human body odor levels where the cost would be worth the benefit.
The bottom line is scent control is an effective tactic in a variety of situations. Its a tool in your tool box. You can choose to use it or not. In some situations it can be very helpful and in others it isn’t. It can give you that “one more step” opportunity that you otherwise wouldn’t get. It can also prevent you from pushing deep into a swamp or a large area of public land. The big thing is it doesn’t have to be an all or nothing approach to your entire season. Use scent control in situations you think it would beneficial but don’t limit yourself with that one tactic. Use the wind because the reality is that if the air current that contains your odor never makes contact with the deers nose they will not smell you (not withstanding ground disturbance and contact odor). Choose your strategy, try different things and implement what tactics you feel are going to help you accomplish your goals.