"Minimizing Human Odor Is Paramount to Hunter's Success" Part 1
By Barry Swanson
We as humans can and do omit odors at any given time. Any hunter who had been winded by a deer- which is to say all hunters- will attest to the stomping, snorting, high-tail-it-out of there response to that first whiff. Whitetail deer can smell at least 25 times better than a human with their 5 million scent receptors. So with that said, the first and probably the best, rule of hunting is to get down wind. But sometimes the wind shifts or the animal moves or the hunter is stationary and the game picks its approach. And sometimes there is no perceptible wind, in those cases we cross our fingers and pray to the Gods of scent thermal dynamics not to betray us. More often than not our prayers are ignored. So what can we do? "Minimize Human Odor" But make no mistake this is far from being an easy task. Scent, and an animal's ability to detect it, are complex phenomena.
Why Do We Smell?
Humans produce an aroma through several different mechanisms; vestigial scent glands are one. Our breath is another. Our sweat is a third. Our hair is a fourth, and our constantly shedding skin is a fifth. Now let's take a look at each.
Scent Glands- we have what are thought to be vestigial scent glands concentrated in the armpits, the anal genital region, around the nipples, on the scalp, and around the eyes. These glands, a specialized type of sweat gland, are called apocrine glands and do not develop until puberty. Aprocrine glands may secrete pheromones, chemical signals that can pass from one individual to another. If they do, animals can probably smell them. Apocrine secretions also carry fats that are enzymatically decomposed by bacteria, producing aliphatic acids. These acids are smelly organic compounds, three of which, caproic, caprylic, and capric. Chemists refer to as the "goat acids". They are the culprits in the condition we laymen know as funk.
Breath- remember with each breath we exude an odor, sometimes mild, sometimes foul beyond belief and if it's foul to us, imagine how it smells to game? Some medical conditions can contribute to this stench, and in fact breath smell can be used diagnostically.
Sweat- the average person has two to four million sweat glands, which secrete colorless liquid that rises to the surface of the skin and evaporates. This process cools the skin to regulate body temperature. On a hot day we can produce two to three liters per hour. While sweat is sterile and odorless to humans, animals may be able to detect trace amounts of ammonia and other chemicals. Moreover, heavy sweating produces the warmth and moisture in which bacteria thrive and the more bacteria on our skin, the more stench they produce. Hair- at the base of each hair follicle is a sebaceous gland, which produces sebum, a compound that waterproofs and oils the hair and keeps it relatively free from foreign nastiness that would like to grow on it. Some people have over active sebaceous glands which, when combined with bacteria produce a greasy, smelly build-up.
Skin- a snake sheds its skin all at once. We shed ours bit by bit. The average person sloughs off 40,000 bits of skin (called scurf or rafts) each minutes. In a lifetime we each shed about 45 pounds of skin. Our skin serves as the residence for millions of bacteria (in the armpit, approximately 2.41 million per square centimeter) which tag along on scurf as it gently floats to the ground on our bodies and in the air. On the ground those bacteria produce their goat smell. We can reduce the number of bacteria hitch hiking on our bodies, but we cannot eliminate them. When surgeons scrub before operating, they remove or kill many of the bacteria on the surface of their skin. But the more they scrub, the more they dredge up new bacteria from within the epithelium. So there is a point of diminishing returns.
How animals smell us!
Scientific research on the ability of wild animals to detect odors is minimal. But a good bit of work has been done on the dog's sniffer, because dogs can be taught to respond to olfactory stimuli and because search and rescue people and the DEA guys at the Miami Airport are interested in how well dogs smell. From findings we can extrapolate, to a degree, what a deer or bear or even fox and coyotes might smell, and how they might smell it. Dogs detect scent that is carried on thermal currents and scent that is on the ground. The airborne scent is comprised primarily of volatile molecules of aliphatic acids. A dog can detect concentrations as low as one part in 10 quadrillion. The ground scent comes from aliphatic acids that leak through our boots, even through rubber boots (a dog has detected the scent of a person eight minutes after putting on a new pair of 0.2-millimeter thick rubber boots). Secondarily we produce a ground scent downwind of where we walk a trail of smell, created by our constantly shedding scurf and it's bacteria hitchhikers.
More in Part II next month!
Barry is an outdoor writer and seminar speaker, and regularly writes for the United Bowhunters of Pennsylvania Magazine.