Bowhunting the Whitetail Rut
With the whitetail rut rapidly approaching in many areas, this column will be specific to this unique and exciting time. I suspect many of you use urine-based scents such as “doe in heat” in attempts to lure that buck-of-a-lifetime into bow range. Like me, you probably have had both good and not-so-good success with these products. You might even be able to recall the morning that big buck came “bird dogging” into your setup like he was “on a string.” But I’ll bet you didn’t know the real dynamics behind that response, an element of whitetail behavior that happened to be the key focus of my Master’s research at the University of Georgia (UGA).
For the past two decades, studies conducted at UGA have attempted to unravel the mystery of how an estrous doe advertises her readiness to bucks in the area. Given that estrus or the “heat” period occurs only once per month and lasts only 24 to 36 hours, the mechanism must be efficient. Hunters have long believed that urine was the source of the magical pheromone or scent that conveys this message. This is a reasonable assumption given that bucks perform the flehmen or lip curl behavior almost exclusively in response to doe urine during the breeding season. When bucks encounter doe urine, they take it into their mouth, lay their head back, and “pump” the urine into a special, diamond-shaped organ in the roof of their mouth called the vomeronasal organ (VNO). Surely, a specialized behavior such as this must be how bucks determine estrus status.
During my research project I 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. The estrous urine and estrous vaginal secretions were collected immediately upon determining a doe was in heat using a vasectomized “teaser” buck. The mid-cycle compounds were collected 14 days later when estrous pheromones are believed to be nonexistent. One buck and two does were used in each trial. The ovaries were removed from all test does to eliminate the possibility of them producing reproductive odors. One of the four compounds was attached to the rump of one doe, and water (the control) was attached to the other doe. The three deer were then released into an outside pen, and the responses of the buck to each doe were monitored.
My results supported those of a prior student who found no significant differences in buck responses to either of the urine treatments. 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 also supported previous research. While there was no significant response to the mid-cycle vaginal secretions, there was a significant response to the estrous vaginal secretions. Bingo! It appeared we were onto something.
Another UGA study confirmed that bucks could easily identify an estrous doe even when their VNO was rendered temporarily inoperable by numbing with Novocain. In yet another study, a “Y”-maze, similar to those used in rodent experiments, was used to determine if a buck could determine estrus status through airborne scent alone. In this study, one estrous doe was placed in one of the short arms of the “Y” while a non-estrous doe was placed in the other. Then, a buck was released into the long arm of the “Y.” The “Y”-maze was fully enclosed, so the buck couldn’t see either doe. As he approached the juncture of the “Y,” the buck was forced to choose which direction to take – toward the estrous doe or the non-estrous doe. The majority of bucks consistently selected the estrous doe.
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 that this scent is emitted into the environment and picked up by bucks through their noses. But what about the role of the flehmen behavior and the VNO? Researchers have discovered that the VNO is connected to a primitive portion of the brain that does not control immediate behavior as in, “Hey there’s a doe in heat in the area,” but instead affects production of reproductive hormones. In contrast, a buck’s nose is connected to the neocortex the behavioral center of the brain. Given this, researchers are now fairly confident that the VNO and flehmen behavior keep bucks sexually “primed” during the breeding season. In essence, it’s their daily dose of Viagra! Interestingly, researchers also have observed that once a buck finds an estrous doe, they will invariably lick the tarsal gland and the “business-end” of the doe (if given the chance!). This licking is then followed by a flehmen response. Perhaps this serves to confirm what they their nose told them, or perhaps it helps further prepare them for the final act. Clearly, we still have much to learn.
What does all this mean to the bowhunter? The take-home message is that when urine-based scents are used appropriately they can work, but maybe not for the reason you originally thought. Urine is an important medium of communication among whitetails, and bucks in the rut are constantly on the prowl for anything that might be female. Doe urine may tell a buck that a doe is in the area, but it probably isn’t the primary mechanism bucks use to locate a doe in heat.
You might be wondering what type of scent I use? In most cases I don’t use any, preferring the scent-free approach. However, on occasion, and especially while bowhunting, I’ll use a doe-in-heat or dominant-buck urine product to stop deer in specific spots. Good hunting!
Quality Deer Management Association
Originally posted 2010-10-13 16:33:42. Republished by Blog Post Promoter