Text & Photos by Tommy Kirkland
-- Whitetails possess an amazing sense of smell and execute diverse forms of scent communication during the pre-rut and rut. These behaviors allow them to pronounce their presence and instinctively prepare them for the breeding cycle. By far, besides tree rubs and scrapes, the "lip curl" is consistently displayed by rutting bucks and is actually an indicator that the pre-rut has begun.
The woodlands are bustling. The cool autumn air stimulates wildlife, causing them to forage for nutrition. Along the slope, a small herd of white-tailed does hesitate and keenly observe approaching movement. A healthy buck with its nasal passages to the ground has the does on alert. Slowly, the buck proceeds toward the females, and as the does move away, the male investigates by scent and sight where they were feeding.
The male deer uses its nose and mouth to pinpoint where a doe urinated. Shoving his snout to the ground, the stag gets the female's urine to make contact with its mouth. Then the buck raises its head and neck upward - and holds this position toward a gentle breeze.
The buck has just displayed what is known as "lip curling" or "flemen." Yet, what is really taking place by this natural act? Is the buck actually scenting doe urine with its nasal organ or is another unseen body part at work here; and why do bucks lip curl doe urine periodically throughout the year - but mainly during the pre-rut and even into the rut?
As bucks traverse fields and woodlands with the onset of the pre-rut, they are, by eyesight and smell, searching for females. When doe urine is located, a buck will take its nostrils and mouth to the excreted urine. The buck then works its tongue - all around its nose and mouth, taking in more doe urine. Although its acute nasal passages are working, the buck is also attempting to get the urine to enter its mouth. This is done by raising its head upward toward the sky - roughly to a 45-degree angle.
Once this position is achieved, the buck then inhales the doe urine by flaring its nostrils and curling the upper lip. The buck's chief objective here is to get the urine to make contact with an organ inside its mouth. This organ is referred to as the vomeronasal. By instinct, the vomeronasal organ helps bucks determine a doe's breeding receptivity. Biologists believe this organ works with a buck's brain and dictates mating behaviors, while stimulates hormonal changes in bucks for the rut.
Surprisingly, although this organ plays a role in helping bucks to instinctively determine if a doe is ready to mate, deer researchers who removed the vomeronasal organ in captive deer found that bucks were still able to distinguish receptive breeding does. This shows that other physical attributes are at work in the whitetail's breeding phase. Physical gestures displayed by does obviously give rutting bucks the visual stimuli needed as well. Yet without scent capabilities and the vomeronasal organ at work, the complex process of whitetail breeding wouldn't be possible - especially in free-ranging deer that cover vast areas to breed.
Although there is usually a pattern for lip curling behaviors, there are slight variations in how bucks perform this natural behavior. If the doe's excreted urine is faint, a buck is more inclined to raise its head and neck stretching upward to a near 90-degree angle with its body. This extreme stretch allows the buck to get more air flow into its mouth, as well as getting the doe urine to reach the vomeronasal organ. Also, certain bucks just tend to display more dramatic behaviors than others. Simply, their lip curls and other rutting action is more intense.
Rutting bucks that may be aggressively persistent also utilize eyesight to locate doe herds. Once a doe or herd is sighted, the frenzied buck immediately pursues the females - searching for urine on the ground. Assertive bucks may even run at does in an attempt to get them to urinate; thereby, exercising the vomeronasal organ.
As you sit atop your treestand or stay concealed within the blind and patiently wait - when that rut-driven buck appears, know that his instinctive determination to breed will take him to the females. Whether deposited naturally or using scent lures, once a buck gets a good dose of doe scent through the "lip curl," the buck's ready to rival competitors, tear up the ground, and batter trees - signaling its dominance. In turn, lip curling behavior sets the stage for more rutting action, the whitetail "scrape," the topic for next month's article.