With white-tailed deer, glandular secretions and scent-marking play a more important role in communication than do visual signals and vocalizations. The latter serve only immediate, short-range purposes, whereas scent-marks serve as an extension of the animal itself, and remain functional long after the maker has left the scene.
Mature whitetail bucks scent-mark vegetation year-round, usually in a subtle manner which is difficult to detect. During autumn, however, they establish highly visible “signposts,” referred to as “buck rubs” and “scrapes.” The hunter who can learn to interpret these signs will add considerable self-satisfaction, if not greater success to the hunt.
The Social Role
Few buck-rubs are made while removing antler velvet, a process normally completed within 24 hours. Instead, most rubs are made by relatively few dominant bucks to advertise their superior social rank, allowing them to signal their readiness to mate and proclaim dominance in a given area.
Signpost rubs are eye-catching, and they are anointed with the maker’s distinctive odor. All whitetails possess specialized forehead skin glands that become especially active during autumn, but tests indicate mature, socially high-ranking bucks exude greater amounts of the glandular secretion as compared to younger males and females. Because rubbing is done with the antler base and forehead, each rub carries the distinctive identifying odor of the maker.
While prime-age, dominant bucks are the primary signpost makers and message “senders,” young males and females are attracted to the signposts and are the message “readers.” The chemical signals exchanged tend to suppress the aggressiveness and sex drive of young males, but stimulate females and help synchronize breeding. As a result, the presence of older bucks and their signposts help maintain social order.
When in the mood, bucks will rub just about anything, including fence posts, powerline poles, and even boulders. Given a choice, however, they prefer to rub trees and shrubs, one-half to four inches in diameter, with smooth bark and no lower limbs. They generally avoid those with low limbs and warty bark.
Trembling aspen is by far the most highly preferred species for rubbing in the Upper Great Lakes region. In the smaller size classes, it has smooth soft bark that is easily stripped, and the inner wood is very light colored, with long-lasting brilliance once exposed. Staghorn sumac, red maple, black cherry, balsam fir, pines, and willows are also frequently rubbed, whereas sugar maple, ironwood, beech, and paper birch are usually avoided.
All bucks occasionally rub stems smaller than two inches in diameter, whereas only older bucks normally rub trees six or more inches in diameter. In addition, young bucks seldom re-rub the same stem. So, large diameter trees that show frequent rubbing (“traditional rubs”) are a sure sign that older, rut-experienced bucks are in the area.
The timing of velvet shedding, and subsequent rubbing, is physiologically controlled and triggered by the shortening day length in autumn. Peak velvet shedding dates normally vary by only a few weeks throughout the United States.
On northern range, bucks generally rub off velvet during late August or early September, nearly two months before the first does breed. Some yearling bucks and unhealthy older individuals are delayed by several weeks.
Mature dominant bucks maintain year-round supremacy over their peers and control a stable male society within a given area. They began marking their domain soon after shedding velvet, without much prior combat or testing, and continue marking until they cast their antlers.
Therefore, serious signpost rubbing in September is evidence of a big buck’s presence. Conversely, delayed and low level rubbing can be expected where antlered males are heavily harvested and few survive to maturity.
Prime-age bucks are the first to reach threshold levels of testosterone that cause velvet shedding. They also achieve higher concentrations of the hormone, which contribute to their extreme aggressiveness, attainment of higher social rank and tendency to make more rubs.
Rub densities in any given area will depend upon many factors. Research shows rub densities even change from year to year, depending upon the nutritional status of the deer herd. For example, more rubs are made during years when acorns (an important autumn deer food) are abundant.
On good deer range, buck-rub densities may vary from a couple hundred to nearly 5000 per square mile, and will be closely related to the number of older bucks in the population. A fairly large number of young bucks may make relatively few total rubs, as compared to only a couple of older bucks in the same area.
Soon after rubbing off velvet, a dominant buck shifts his center of activity to interact with other deer over a breeding range of anywhere from one to six square miles. Bucks on northern range tend to travel a large autumn range when deer density is low, whereas they’re more apt to cover less area where deer are plentiful.
Clusters of buck rubs most likely occur in habitats close to areas with abundant autumn food. This could be wooded cover near corn or alfalfa fields, oak habitat when acorns are abundant, adjacent to forest openings, or near artificial feeders and food plots. Such a rubbing strategy makes good sense because other deer would also likely concentrate near such choice feeding sites, making the buck’s signposting most effective.
Also look for rubs along travel corridors such as deer trails, ridge tops, old logging roads, and in swales at stream crossings. Clusters of rubs in secluded patches of heavy cover may also reveal the favored bedding location of older bucks. Stand hunting along travel corridors, between bedding and feeding locations, will generally prove the most successful.
The presence of mature bucks and the availability of favorable rubbing stems are primary factors determining buck-rub density in any given area. In fact, some researchers speculate that clumping of rubs is primarily related to location of preferred stems. Therefore, while a scarcity of buck-rubs can generally be attributed to a lack of older bucks, sometimes it may be due to a scarcity of preferred rubbing stems.