For an avid hunter, avoiding the white flag is critical in the pursuit of the whitetail deer. A whitetail’s nose is 4,000 times more effective at distinguishing scents then a human, according to Missouri Conservationist Online.
A whitetail deer’s best defense mechanism is its nose. Scents connected with humans are a warning signal to deer and other big game animals, a red flag saying, “stay away!” Therefore, reducing the trace of human scent is critical in the pursuit of big game.
By Adam Mohnen
Knowing this, I set about testing scent killers. After walking into the local sporting goods store and looking online to purchase scent killers, I was overwhelmed. With so many brands to choose from and their high prices I wanted a second opinion.
While searching the web I came across numerous hunters speculating that all scent killers are a combination of water, baking soda, hydrogen peroxide and that’s what we are spending big bucks on each year to reduce odor causing bacteria in the woods.
This raised questions. Are we paying that much money each year for just water, baking soda and hydrogen peroxide? If not, what are scent killers made of? Some scent killers don’t even list the product ingredients on the bottle.
With these questions and not many answers, I had only one option. I set up and conducted a lab with the help of Lance Rohan, another hunter, and James Schultz, a high school biology teacher.
This lab was designed to grow odor causing bacteria from three of the four main odor causing bacteria sources: the foot, the armpit and the groin. Each source was swabbed one-by-one using a separate q-tip and was swirled into a test tube filled with nutrient broth, a food source for bacteria to grow the odor causing bacteria.
In an effort to determine which scent killers work best in killing human odor-causing bacteria, 11 different scent killer products were used in a lab to compare each substance’s zone of inhibition to see which product is the most effective in killing bacteria. The zone of inhibition is the ring around the filter paper disk where the bacteria was killed.
Some hunters speculate that companies are marketing a diluted solution as scent killer. This speculation has led them to research and develop home-made scent killers. For this reason, two homemade scent killers consisting predominately of hydrogen peroxide and baking soda were used in this lab.
Based on my first hand hunting experience using scent killing products, and following the scientific method I predicted the following conclusion: if 11 different scent killing products are all tested on bacteria from the human armpit, foot and groin, the zone of inhibition from largest to smallest will be: Scent Killer shampoo, Old Spice body wash, Scent Killer Original Formula, Scent Killer Autumn Formula, Carbon Blast, Dead Down Wind (evolve3), Primos Silver Scent Eliminator, Scent Shield, Scent-A-Way Original Forumla, homemade scent killer (with soap) and homemade scent killer (without soap).
A q-tip was used to swab three major bacterial sources: the armpit, groin, and foot. Three separate q-tips were used to gather bacteria by rubbing the q-tip in small circles for five seconds. After the swabbing process was complete, each of the three q-tips was swirled in a test tube containing 10ml of nutrient broth. Once the nutrient broth contained the bacteria, the test tube was placed into an incubator and cultured at 37 degrees Celsius, the temperature of the human body, for 24 hours.
Following the 24 hour waiting period, a pipette was used to mix the bacterial growth and nutrient broth to provide common consistency throughout the mixture. Six drops of the nutrient broth mixture was placed in the middle of each of the six 8.75cm Petri dishes that contained a layer of nutrient agar, another bacteria food source, on the bottom of the dish. A fresh q-tip was used to gently spread the nutrient broth mixture over the nutrient agar to the edges of each Petri dish.
At this point, the odor causing bacteria has been grown just as if it was on your body. Next the scent killer options will be added. Using a 6mm hole punch, 24 filter paper disks were punched out and dipped respectively in each of the 11 scent killers with a tweezers and placed into its own pre-marked quarter of each of the six Petri dishes.
This process was repeated two times with each substance. The tweezers was rinsed with water and dried with paper towel between handling of each paper disk. All six Petri dishes were cultured in an incubator at 37 degrees Celsius for 24 hours.
After 24 hours, the six dishes were removed from the incubator and the zone of inhibition, the ring around the filter paper disk where the bacteria was killed, was measured using a plastic ruler and recorded for each of the eleven substances. The two leftover quarters in the last Petri dish were used to repeat one individual experiment due to a possible error on the first trial. This served as a control to check for consistent results.
Contrary to the original hypothesis, Scent Killer shampoo did not have the largest zone of inhibition. As shown in graph one, Scent Killer shampoo’s zone of inhibition was 9mm smaller in diameter than Scent-A-Way Original formula, the most effective product.
Due to the inability to obtain the ingredients used in Scent-A-Way Original Formula it is unclear why it preformed so distinctly. The active ingredients were not able to be compared with the product with the second highest zone of inhibition, Primos Silver Scent Eliminator. In fact, three of the top four store bought scent killers did not list their ingredients. This could be because the companies do not want their products illegally duplicated.
The homemade scent killer with soap consisting mainly of baking soda and hydrogen peroxide, had a zone of inhibition of 14mm and preformed better than six other store bought products (shown in figure one). Homemade scent killer without soap, with a zone of inhibition of 8mm, also performed better than five store bought products including Scent Killer Original and Autumn Formulas (shown in graph one). If the zone of inhibition was 6mm, then the product had no real zone of inhibition due to the disk size of 6mm that was included in the zone of inhibition measurement (table one).
The following all had zone of inhibitions of 6mm; Carbon Blast, Scent Killer Original and Autumn Formulas, Scent Shield Original, and Dead Down Wind (evolve3), suggesting these products simply mask human odor rather than eliminating odor causing bacteria.
Old Spice body wash was used as a positive control because it is a common product used to kill bacteria on a daily basis. Water was a negative control because bacteria thrives in water. Two separate tests were done on each substance to compare results and eliminate any outliers.
Based on these tests, I plan on switching my personal scent killing products to Scent-A-Way Original Formula and Primos Silver Scent Eliminator due to their effectiveness in killing human odor causing bacteria.
The next time you are in the woods ready to draw back or pull the trigger, avoid the white flag and the feeling of defeat. Use the information provided to choose a scent killer for your next hunt. If the scent killers cost too much, take the time to whip up a quick batch of your own before your next hunt. An easy recipe can be found on the internet with a quick Google search for “homemade scent killer” to apply on clothing and gear.
Homemade Scent Killer Recipe (Used in this lab)
– 1 used/clean plastic milk jug
– 1 large mixing bowl
– 16 oz. (2 cups) Peroxide (3%)
– 16 oz. (2 cups) Distilled Water
– ¼ cup baking soda
– 1 oz. unscented shampoo (Hunter’s shampoo)
– 1 spray bottle
Mix the peroxide, distilled water, baking soda, and shampoo in a large mixing bowl until baking soda dissolves, then pour the mixture into the milk jug and let sit. After letting the milk jug sit for a few days, pour some into the spray bottle and use as needed.
• Pressure will build up in the milk jug. Make sure you do not tighten the cap all the way allowing the pressure to escape.
The circle area around the filter paper disk is the zone of inhibition. Each substance was checked 24 hours after it was placed in the bacteria. In some of the zones of inhibition there are little spots of bacteria. These are called satellite colonies.
Satellite colonies are formed because the effectiveness of the scent killer has “worn off” in certain spots. In the scent killer shampoo there are a few satellite colonies, but you should take a shower in scent killer shampoo before you go on each of your hunting adventures. If there is no area of inhibition around the filter paper disk, then the scent killer was ineffective at killing human odor causing bacteria such as Dead Down Wind, which failed to kill human odor causing bacteria. In contrast to Scent-A-Way Original Formula which out preformed the competition.
*The zone of inhibition of both trials were averaged together.
*The filter paper disks used had a diameter of 6mm. Also the zones of inhibition in both tests were averaged together.
Cwynar , T. (2001). Deer Hunting Basics. Retrieved December 8, 2008, from http://mdc.mo.gov/conmag/2001/10/40.htm
This story originally appeared in 2009.
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