Text & Photos by Tommy Kirkland
Although there are different forms of scent communication with whitetails, pre-rut and rut are two of the most significant for deer. To establish a dominant presence amongst competing bucks and to attract females to a scrape site, bucks will paw the ground vigorously with their front hooves - releasing scent from glands in the hooves called "interdigital glands."
-- Scent pheromones are instinctively utilized by whitetails to convey a realm of communication related to dominant hierarchy and sexual interactions. They are crucial for other social interactions - particularly for females raising their offspring. These scents are produced by several different glands located on the animal's body and serve deer of all ages and sex.
The most common glands by far are the tarsal glands, which are located inside the rear legs of both bucks and does. Tarsals are believed to be the prime calling card for whitetails to distinguish themselves. The scent released from the tarsals may enable whitetails to identify not only the sex of a particular deer, but the age as well.
During the pre-rut, bucks really begin to put their tarsal glands to work - especially at scrape sites. After working an overhanging licking branch and pawing the ground with the front hooves, bucks will then perform what is known as rub-urination. Basically, a buck will bring its tarsal glands of both legs together and urinate on them while simultaneously rubbing its rear legs and hindquarters - stimulating the tarsals and depositing scent upon the ground.
While this behavior is not yet fully understood, it is believed that rub-urination on tarsal glands allow deer to identify one another. Dominant bucks use tarsal rub-urination to announce their presence - particularly in the pre-rut. Whitetails of all classes - young, old, female and male will periodically perform rub-urination on their tarsals throughout the year.
Observations afield strongly indicate that the most assertive and aggressive bucks are usually pungent with a strong tarsal odor produced by the tarsal rub-urination process; and have some of the darkest stained glands. One reason for this smelly distinction is that these dominant bucks are constantly working the tarsals.
Usually after pawing the ground, a rutting buck will bring its rear legs together and urinate on the tarsal glands, which are located on the inside of the rear legs. While urinating, the buck also moves and rubs the tarsals together. This is believed to help stimulate the scent being released, and the urine mixes with it to create a very pungent odor. This particular scent allows deer to identify one another. The tarsals are also referred to as "hocks."
Biologically, when bucks perform rub-urination, there is a composition with bacteria and the urine; and it is believed that fat lipids are released during rub-urinations. These factors may contribute to the strong odor. Finally, genetics and testosterone levels could also play a significant role in why one buck's tarsal glands are darkened more than another buck's tarsal glands.
The next set of glands in the whitetails' arsenal of communication are the interdigital glands located between the hooves of both the front and rear legs. These glands, like the tarsals, are also a major contributor to distributing scent for rutting bucks, which paw the ground through scrape behaviors.
Being that each deer scent is individually distinguished, scent released from the interdigital glands helps deer to follow or locate one another - especially rutting bucks in pursuit of females. These glands allow whitetails to form scent travel routes and assist in establishing their home ranges. This is crucial for herd socialization and for females raising their young. These glands are believed to be the foremost way whitetails track one another.
In addition, another major set of whitetail glands are found on the forehead. Like the interdigital glands, forehead glands assist rutting bucks with depositing scent through tree rubs and the marking of overhanging branches. The scent from the forehead glands of dominant bucks is vital for the mating process and is believed by some biologists to trigger females into heat. The forehead glands are actually seated between a buck's eyes and antler base.
The next gland on the whitetails' palette is the pre-orbital gland. Located near the eye pit toward the nose, the pre-orbital gland may be used on an overhanging branch during a buck's scrape. Most experts believe the gland serves other purposes related to buck aggression and is most likely a tear duct.
The whitetails' salivary glands inside the mouth may help bucks spread scent at overhanging licking branches for scrape marking. A buck will slam its forehead glands and antlers into a rubbed tree. Periodically, a buck will lick the shredded tree thereby utilizing its salivary glands.
Bucks will periodically batter trees by rubbing their antlers and forehead glands into the tree bark. This function allows them to deposit their scent - signaling their presence to other deer. Although tree rub signposting is a form of scent communication like scrape sites, bucks also rub trees with aggression; and it is believed that they are preparing for upcoming battles with rival bucks.
Recent studies into whitetails working overhanging licking branches at scrape sites are now beginning to conclude that the nasal gland contributes to scent communication as well as to serve as lubricating moisture for the airway.
Other glands that deer have are the metatarsals located on the outside of the hind legs - yet they are not really glands. The purpose of metatarsal glands remains a mystery, but some biologists believe the glands could influence the instinct of flight with what is called exteroceptive sensory - picking up on external stimulus sources, possibly allowing deer to detect vibrations. This is purely speculative in relation to this poorly understood gland that is more of a duct than a gland.
All male deer possess preputial glands that are internal to a buck's penal sheath. Its primary function is lubrication for this genital area. Biologists from the University of Georgia, particularly Dr. Karl Miller, think this gland may produce pheromones that contribute to a buck's rutting odor.
All these glands are vital for whitetails to survive; yet deer also use other physical attributes in combination with scent communication. Simply, the nose and eyes work to pinpoint scrape sites and previously rubbed trees while organs like the vomeronasal work to instinctively determine if a doe is in estrus.
Overall, the whitetails' world of scent communication is complex; yet by learning the role of each gland, sportsman will not only appreciate the creature hunted, but also gain a better understanding when examining sign, traveling routes and all the signpost activity left by whitetails as they traverse the land.
--Text & Photos by Tommy Kirkland
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