You’ve likely seen it in action or assumed its presence, but do whitetails really have an extra sense? The science says yes.
It will probably come as no surprise to most hunters that scientists have identified a sixth sense in whitetails. No, it’s not their ability to read your brain waves or spot you while sitting upwind and motionless high in a tree. This sixth sense does, however, play an important role in whitetail communication and reproduction—essential elements for ensuring survival of the species. Before discussing this interesting sense, keep in mind that the five basic senses that whitetails share with humans include touch, taste, smell, hearing and vision.
Inside The Sixth Sense. While many hunters have observed bucks using this “extra” sense, few understand how it works or what role it plays. Known as vomerolfaction, this sense is similar to taste and smell, though it involves a very specialized structure known as the vomeronasal organ—or VNO for short. This diamond-shaped organ is located in the roof of the deer’s mouth and is used exclusively to analyze other deer’s urine. The most common example of vomerolfaction occurs when a buck encounters the urine of a doe during the breeding season. The buck will lick the urine, tilt its head back, grimace, and perform what is known as a flehmen, or lip-curl behavior. This process causes muscle contractions around the VNO and creates a weak vacuum that forces urine into the VNO. Since this behavior is almost exclusively restricted to bucks during the breeding season, it was long considered the process through which a buck determined the estrus status of a doe. However, recent research suggests a different role.
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Researchers at the University of Georgia have conducted numerous studies on how bucks determine a doe’s estrus status. These studies have revealed a complex system involving both scent and behavioral cues to ensure that breeding occurs in a timely and efficient manner. From a scent perspective, secretions from the doe’s reproductive tract appear to be the primary source of the magical “scent of estrus.” Several studies, including my own graduate research years ago, have attempted to determine if these scents—known as pheromones—also were present in a doe’s urine during estrus. To date, little evidence supports their presence in urine, at least at levels high enough to elicit measurable interest among bucks. From a behavioral standpoint, it is well documented that a doe will rigorously avoid courtship approaches from bucks until she is in peak estrus and ready to breed. This state of “standing estrus” is all a buck needs to mount a doe, regardless of any pheromones she may be emitting at the time. In other words, if a doe—or even a doe decoy—stands still long enough during the breeding season, a buck will mount her!
Role Of Vomerolfaction In Whitetail Reproduction. Given these findings, what role does research suggest vomerolfaction plays in the breeding process? To explain this, it is first necessary to understand the deer’s brain. A deer’s main olfactory system (its nose) is connected to the portion of the brain that controls immediate behavior. As such, “the scent of estrus” either from a doe’s reproductive tract or through airborne scents, can elicit an immediate behavioral response from a buck, such as “there’s a doe in heat nearby, I must locate her now!” In contrast, the VNO is connected to the portion of the brain that controls reproductive physiology, or a buck’s interest in breeding and its physical readiness to breed. This process is not immediate, but instead takes time for the signals from the brain to stimulate the buck’s reproductive organs. In simple terms, the process of vomerolfaction appears to be similar to a buck taking a regular dose of Viagra. This maintains his breeding interest and readiness, rather than conveying immediate information regarding a particular doe’s estrous status.
What’s The Bottom Line For Hunting? Given that neither a doe’s urine—nor a buck’s analysis of this urine through vomerolfaction—appears to be the primary mechanism through which a buck determines a doe’s estrus status, does that mean that urine-based scent products are not useful for hunting? Not at all. Urine remains one of the most-important means of communication among deer. A buck seeking an estrus doe during the breeding season often will investigate the scent of any doe in the area, regardless of her estrus status. In addition, the research remains unclear regarding whether any estrous information is contained in naturally voided urine. The bottom line? If it works for you don’t stop using your favorite urine products. Armed with this latest Whitetail Science, at least now you have a better understanding of the whitetail’s sixth sense and its role in reproduction.
