Making Sense of Scents

Deer communicate with each other through scents that hunters try to replicate. Here’s how to make sure you’re saying the right things.

Cliff Covington

December 02, 2008 at 2:35 pm  | Mobile Reader | Pring this storyPrint 

When a hunter drops a rutting buck that has a strong odor, most of that originates from the tarsal gland, which is inside of the deer’s hind legs. These glands secrete lipids that cling to the long hairs.
When a hunter drops a rutting buck that has a strong odor, most of that originates from the tarsal gland, which is inside of the deer’s hind legs. These glands secrete lipids that cling to the long hairs.
Without a doubt, the sense of smell is the most important physical perception available to the white-tailed deer. Deer rely heavily on their noses to detect the presence of predators and locate food sources.

However, communication with other deer is where scents play their most important role. Through the use of scents, deer have the ability to recognize other deer and identify the other deer’s sex, its reproductive state, its dominance status and much more.

It is extremely difficult for humans, living in a sight-oriented world, to grasp how important the sense of smell is to white-tailed deer.

“One of the best ways to get an idea of how deer communicate with scents is to look at the different glandular areas on the deer,” said Karl Miller, a University of Georgia deer biologist who is also a renowned expert on deer physiology and senses. “So far, we have identified seven different glands or glandular areas on deer, but as we continue our research, we will likely discover more.”

Before we get into the specifics of commercially produced deer scents and where they fit in, let’s first take a closer look at a few of these glands and identify their purpose.

Tarsal gland

Any hunter who has harvested a buck is familiar with this gland and the strong smell associated with it. Located on the inside of the deer’s hind legs, this gland is by far the most important to whitetails. It is comprised of a tuft of elongated hairs that is underlain by an area of enlarged subcutaneous glands. These glands secrete a fatty substance, referred to as a lipid, which clings to the long hairs.

Most hunters assume the foul odor is produced by the tarsal glands. However, nothing could be further from the truth.

According to Miller, the smell comes from urine deposited on the tarsal gland in a behavior called rub-urination. As the urine flows over the tarsal gland, the fatty substance secreted from the glands onto the long hairs selects particular molecules in the urine and holds them on the gland. The portion of the urine remaining on the tarsal gland reacts with the air and with bacteria to produce the gland’s distinctive odor.

“Clearly the tarsal gland is used by deer to recognize individual deer,” said Miller. “Deer often sniff the glands of other deer. By doing so, they not only can tell who the other deer is, but also learn about the other deer’s sex, dominance status and condition. Rutting bucks use this gland to advertise their dominance status and breeding condition both to other bucks and does.”

Metatarsal gland

Located on the outside of the deer’s hind legs, the metatarsal gland is identified by an oval ring of whitish hairs surrounding a black callous area. Large numbers of enlarged sebaceous glands are found in the area under these hairs. Researchers have been unable to determine what function, if any, this gland plays in deer communication.

“In mule and black-tailed deer, this gland is much larger than in whitetails, and has been shown to be the source of an alarm pheromone (scent) that can alert other deer in the area to the presence of danger,” Miller said. “Although it is possible that this gland serves the same purpose in whitetails, we think it is vestigial. This means that eons ago, it may have had a purpose, but now it is slowly fading away.”

Interdigital gland

The interdigital gland is located in the cleft between the toes on all four feet of both bucks and does. This small, sparsely-haired gland secretes a yellowish, cheesy material that gives off a foul, rancid odor. Some of this scent is left in the deer’s track each time it takes a step.

Based on research at the University of Georgia, the secretions from the interdigital gland contain a variety of small molecules called volatile fatty acids. The researchers also found that these molecules evaporate at different rates. This would cause the odor of the track to change over time, which would also explain how a deer or predator can tell how old the track is and which direction the deer is headed.

Preorbital gland

The preorbital gland, a small pocket located immediately in front of the eye socket, is sometimes called the tear gland, even though it does not produce tears. Deer have muscular control of this gland, and can flare it open at will. Rutting bucks have been observed flaring this gland when signaling their aggressive intents to other bucks. Also, does frequently will open this gland while they are tending their fawns.

“We are not sure whether or not this gland actually produces a scent,” Miller noted. “The opening of the gland may just be a visual display and not an olfactory display.

“Some researchers, and hunters, suggest that the preorbital is used to mark the overhanging branch at a scrape site. Although this may be true, if you watch a buck marking an overhanging branch, you will notice that he appears to be marking it with his whole head — forehead, antlers, nose, mouth and preorbital area. It seems more likely that he is leaving scent on the branch from several areas, which may include the preorbital gland.”

Forehead gland

As the name implies, the forehead glands are located on the buck’s forehead, between his eyes and the bases of his antlers. Research by Tom Atkeson at the University of Georgia indicates that the forehead gland is very important to whitetails. Atkeson has noted that the forehead area of deer contains large numbers of sweat glands that become active during the rutting season. Most researchers believe that this gland is the source of scent left on rubs and overhanging branches at scrape sites during the breeding season. All deer, both bucks and does, have this forehead glandular region; however, the most active glands are found on dominant, mature bucks during the rut.

“I have noticed a marked difference in the color of the frontal gland area in bucks,” said James Kroll, recognized worldwide as one of the foremost authorities on white-tailed deer. “Dominant bucks have a much darker appearance than subordinate bucks. Dominant bucks appear to use the frontal gland to mark their territory.

“I have some excellent videotape of a dominant buck rubbing his frontal gland on a signpost, apparently checking it periodically for the right amount of scent with his nose. I feel that much of the so-called antler rubbing reported for bucks is actually forehead rubbing to deposit scent.”

Commercial scents

Now that we know a little more about the scents naturally produced by whitetails, let’s explore the use of commercial scents and their effectiveness.

There are numerous products on the market nowadays that claim to do everything from luring a buck right in your lap to making a mounted deer head come to life with a single whiff of their magic potion.

Does that mean these products work in every situation? Of course not. The key to their success is using the right scents in the right situations.

Basically, there are three types of commercially produced products available: 1) those that mimic deer communication scents, 2) those that mask human scent, and 3) those that neutralize human scents.

“The first type, with a few exceptions, consists of scents that are made from or synthesized from chemicals presumed to affect deer behavior,” Kroll said. “The ‘presumed’ is critical here. At this point in time, there absolutely is no evidence that any of the commercially available scents do indeed elicit the response espoused.”

The results of research conducted by Quality Deer Management Association Executive Director Brian Murphy support Kroll’s contention. In Murphy’s research project, he tested the response of rutting bucks to four substances: 1) estrous urine, 2) mid-cycle urine, 3) estrous vaginal secretions and 4) mid-cycle vaginal secretions.

At this point, keep in mind that most of the commercial scents that mimic deer communication scents are urine-based, with many being a combination of chemicals containing little or no actual deer urine. In fact, some researchers have identified everything from rabbit urine to water in some of the commercially available scents. The urine and vaginal secretions used in Murphy’s study came “fresh” from a live doe.

“My results found no significant differences in buck responses to either of the urine treatments,” said Murphy. “In other words, the magical pheromone didn’t seem to be present in urine, or was present in such small quantities that it did not elicit a response from the bucks used in my study.

“My results regarding the vaginal secretions were another story. While there was no significant response to the mid-cycle vaginal secretions, there was a significant response to the estrous vaginal secretions.

“Collectively, these studies suggest that a doe’s reproductive tract is likely the primary source of the magical pheromone that conveys her reproductive status. They also suggest the ‘doe-in-heat’ scent is emitted into the environment and picked up by bucks through their noses.”

The bottom line is that when urine-based scents are used correctly, they can work, but maybe not for the reason most of us originally thought. Urine is an important means of communication among whitetails, and bucks in the rut are continuously on the prowl for a “hot” doe. And while doe urine may tell a buck that a doe is in the area, it most likely isn’t the primary mechanism a buck uses to locate a doe in heat.

Buck urine and tarsal glands can also be very effective when used in the appropriate situations. A prime example of the perfect time to use these scents is while horn rattling. A mature buck will be much less cautious on his approach if everything “sounds” and “smells” like two of his competitors fighting.

The second type of commercially produced scent is masking scent. Masking scents come in a variety of forms — skunk musk, raccoon or fox urine, or even various kinds of natural scents (persimmons, apples, acorns, earth, evergreen, etc.). They all work in a similar fashion.

“If you are carrying on a conversation, with a radio playing in the background, your ability to hear what is being said depends on the volume of the radio,” Kroll said. “At some point, the noise from the radio becomes so distracting that you no longer pay attention to what is being said. The conversation is still there, you have just lost your ability to discriminate from it and the background noise.

“So it is with masking scents. Your odor is still there; it is just being overridden by the masking scent.”

Try not to get too fancy with masking scents. The scent needs to mimic something occurring in the deer’s day-to-day world. Any unusual scent will do more harm than good by drawing attention to your location, rather than masking it.

Although skunk is one of the most effective cover scents available, avoid using it while hunting from a ground blind, especially during skunk mating season. A few years back, I was pinned down for almost an hour in my ground blind by none other than Pepe Le Pew and his love-sick cousin Stinky.

Since that time, I have opted to use raccoon urine as a masking scent.

The third type of commercially produced scents are the neutralizing products, which include scent-eliminating clothing. These products have been on the market for several years, and have garnered much acclaim by the hunters who have used them. Basically, their main function is to destroy the odor itself. This is what many refer to as the scent-free approach.

In reality, we all know that hunting scent-free is a misnomer. It is impossible to totally eliminate all human scent while hunting. However, we should always strive to reduce as much human odor as possible. If that means using commercial products that mask, mimic or neutralize scents, then by all means, use them.

Because of a deer’s strong sense of smell, we must remember to always use our most important sense — common sense. Proper positioning and stand placement is everything when it comes to deer hunting. It is critical to hunt downwind of where you expect deer. If you keep downwind of a buck, there is very little chance he will smell you, whether you are using scents or not.

Deer leave scents from preorbital glands on leaves and branches that overhang scrape sites.
This curious doe was harvested as she came in to check out a scent bomb that was hung in a nearby tree.
During the rut, hunters regularly use scent bombs to draw in amorous deer.
   



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