Whitetail Communication; Scents

[T.R. Michels]

Scent Glands and Organs
Deer use scents pheromones and hormones to communicate their type of sex, sexual readiness, dominance, their travel route and direction, and alarm by: 1. self-impregnation (leaving scent on themselves) and, 2. leaving scents on the ground and vegetation, and at the visual and chemical signposts of rubs and scrapes. These scents are so specific that deer have the ability to distinguish individual scent no matter how many other deer are in the area. Glands produce many of these deer scents.

Forehead Glands: The forehead glands are located between the top of the eyes and the antlers. They are most active during the rut. The activity of these glands has been positively correlated with age and probable social status; they are most active in older, dominant bucks. The glands produce an oily substance making the hair appear dark. The oil is transferred to rubbed trees and the overhanging branch at scrapes when the head of the buck comes in contact with the tree; and is used by dominant bucks to advertise their presence to both sexes. Marking trees and branches with forehead scent is a means of dominance and recognition among bucks. It has been noted that dominant bucks create most rubs, and they rub more often than subdominants. The scent from the forehead glands may be used as a priming pheromone to bring does into estrus; and to synchronize the timing of the rut between bucks and does when it is left in areas used by does.

Pre-orbital Gland: Located in front of the eye, this gland is under muscular control and may be opened by rutting bucks to signal aggressive behavior. Females open this gland when tending fawns. It may not be rubbed on the overhanging branch as previously thought.

Nasal Gland: These two almond-shaped glands are located inside the nostrils and are probably used to lubricate the nose. They may also be used to leave scent on overhanging branches.

Vomeronasal Organ: This diamond shaped organ is located on the roof of the mouth and serves some of the same purposes as the nose. It is used primarily to analyze urine, possibly while performing the lip curl and sniff, or Flehmen gesture, when a buck curls its upper lip and sucks air into its mouth so that scents come in contact with the vomeronasal organ. It is usually performed by a buck that is with/trailing an estrus doe. Analysis of urine through the vomeronasal organ may help to synchronize the breeding readiness between bucks and does, and ensure that both sexes are in peak breeding condition at the same time.

Salivary Glands: These glands inside the mouth produce saliva, which contains enzymes to help in digestion. The enzymes in the saliva may contribute to the scent left on the overhanging branch at scrapes, and on rubbed trees when a deer licks or chews the branch or tree.

Interdigital Glands: These glands are located between the hoofs of all four feet of white-tailed deer. The scent is left each time the deer takes a step. It is also left in large amounts when a deer stamps its foot, and when a buck makes a scrape. Each deer has its own scent, and because some of the compounds in this scent may be present in higher concentrations in mature males (3 1/2+ years), they may alert other deer of the presence of a dominant buck. Does use this scent to track their fawns, bucks use it to track does. Because scent molecules evaporate at different rates deer can determine which way another deer went by the amount of interdigital scent left behind. The scent from these glands is the primary tracking scent of deer.

Preputial Gland: This gland is located on the inside of the buck's penal sheath and may be used for lubrication.

Metatarsal Glands: These glands are a light tan colored circle of hair of about 1 2/3 inches in length located on the outside of the hind leg between the toe and the hock, or heel on whitetails. They are not actual glands, because they have no duct. Mule Deer exhibit the largest glands, then the Black-tailed Deer, and the White-tailed Deer. It has been suggested that blacktails open this gland when alarmed to express danger. It is not totally understood in whitetails, but I have seen it flared when two bucks fight.

Tarsal Glands: These true glands appear as a tuft of erectile hairs, measure about 4 inches in diameter, and are located on the inside of the hind leg near the hock. The lactones of these glands are specific, allowing other deer to determine age and sex of the deer leaving the scent. The strong smell of the tarsal gland is caused by the deposit of urine on the deer's gland during rub-urination. Rub-urination occurs when the deer brings the back legs together and urinates over these glands. Bucks rub-urinate to display social dominance by marking themselves with the scent, and they determine social ranking by sniffing each other's tarsal. Does rub-urinate to make it easier for their young to follow them; and possibly to express social status among doe groups. Young animals rub-urinate as a means of self-marking. Part of the function of the scent from this gland may be to act as a warning signal. The scent from this gland is the primary recognition scent of deer.

Urine: Bucks smell estrogen in the urine of females when they are sexually ready to breed. It has been suggested that does smell testosterone and protein levels in buck urine and are able to determine the health of the buck by the smell, which allows them to choose a healthy dominant buck to breed with. The combination of scents left behind during rub-urination at a scrape (urine, testosterone, and tarsal) may serve as priming pheromones to bring female into estrus.
 
    Bucks may form bachelor groups and travel together prior to the rut. They often groom each other’s head/neck region, and know the smell of each other by the forehead, tarsal, metatarsal and interdigital scents. Older bucks exert dominance over subdominants throughout the year by threats; kicking with the foreleg, and attacking with the antlers. When sparring begins in the fall the younger bucks already know which other bucks are dominant and stronger. They also know which dominant used a rub, overhanging branch and scrape by the smell left behind; this eliminates much of the fighting between bucks that might otherwise occur.