The most common glands by far are the tarsal glands. They are located inside the rear legs of a buck or doe. Tarsals are believed to be the prime calling cards for whitetails to distinguish themselves and identify one another.
The scent released from the tarsals may enable whitetails to distinguish 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 the classic overhanging licking branch and pawing the ground with the front hooves, bucks will then perform what is known as rub-urination. Here, a buck will bring the tarsal glands of both legs together and urinate on them while simultaneously rubbing his rear legs and hindquarters, stimulating the tarsals and depositing scent on the ground.
Though we may never fully understand this unique behavior, it is believed that rub-urination allows bucks to establish dominance. Mature bucks use tarsal rub-urination to pronounce their presence and do so more often than younger bucks. Whitetails of all classes - young, old, female, and male - will periodically perform rub-urination on their tarsals throughout the year. Yet this activity really kicks in with the pre-rut.
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.
Biologically, when bucks perform rub-urination, there is a composition with bacteria and the urine, and it is believed that lipids are released during rub-urinations. These factors may contribute to the distinct smelly odor.
Finally, genetics and testosterone levels could also play a significant role in why one buck's tarsals are darkened more than another's.
The next 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 that paw the ground to make scrapes.
Being that each deer scent could be 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, helping them to establish their basic home ranges. This is crucial for herd socialization and for does rearing young. These glands are believed to be the foremost way whitetails track one another.
In addition, another major gland for the whitetail is the forehead gland. Like the interdigital glands, these glands serve rutting bucks 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 is controversial and may not actually contribute to pre-rut scraping behaviors. Although this 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. There is still a lot about this gland that we just don't know.
The whitetails' salivary glands do not produce scent, but it is theorized that when bucks lick overhanging branches or tree rubs, some type of communication is being received or reinforced. The behavior is similar to when bucks periodically lick their tarsals glands. Whether the salivary glands contribute to scent communication is really unknown.
Recent studies into whitetails working overhanging licking branches at scrape sites are now beginning to conclude that the nasal gland may contribute to scent communication as well as provide lubricating moisture for the airway, particularly with cold dry air. These glands do help in locating other deer, and are vital for scent messaging.
Other glands that deer have are the metatarsals on the outside of the hind legs, yet they are not really glands. Their purpose remains a mystery, but some biologists believe they are used with aggression and could be related to 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 a preputial gland that is internal to a buck's penal sheath. Its primary function is lubrication for this genital area.
Biologists from the University of Georgia, particularly Karl Miller, think this gland may produce pheromones contributing to a buck's rutting odor.
All these glands are vital for whitetails to survive, yet deer also use their 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, through lip curling, 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, the sportsman will not only appreciate the creature hunted but gain a better understanding when examining sign, traveling routes and all the signpost activity left by whitetails as they traverse the land.
With hormonal changes under way and as the days shorten, whitetails begin to communicate more intensely as breeding nears. This sets the stage for the pre-rut and influences a change in a buck's normal routine - next month's topic.