Signpost Secrets: Probing the Mysteries of Whitetail Rubs

signpostsCervids (members of the deer family) living in open country, such as elk and mule deer, rely heavily upon visual displays and vocalizations when communicating information of social significance. In contrast, forest-dwelling white-tailed deer more commonly use glandular secretions and scent-marking, especially in conjunction with antler rubs and ground scrapes, commonly referred to as signposts.

By John J. Ozoga, Deer & Deer Hunting contributor

Scent marking and signpost communication is especially effective in dense forest cover, because chemical signals left on objects in the environment remain functional for lengthy periods in the maker’s absence. Typically, especially during the rut, mature bucks make most signposts to advertise their presence. Young males and females are the primary “readers.”

My observations, using fake antler rubs and mock ground scrapes, have revealed that visual attractiveness is also important in determining deer response to rubs and scrapes. In fact, when controlled and manipulated according to study design, the use of artificial signposts permits testing various scenarios that might contribute to seasonal aspects of whitetail signpost formation and visitation.

Unfortunately, the use of artificial deer signposts in deer research has received minimal attention. In fact, other than the work I did, I can find no other scientific publications on the subject.

Longtime Deer & Deer Hunting contributor Charles Alsheimer and I have been discussing various aspects of deer biology for decades, starting long before some of you young hunters were born.
Once, he quizzed me about how he should interpret some of his observations. As I recall, my advice was, “Just call ’em as you see ’em.”

Given the whitetail’s adaptability and extremely flexible behavior, depending upon the environment, and our differing experience, it’s not surprising that Alsheimer and I sometimes disagree on aspects of deer behavior. In fact, my deer research findings often contradict those of other scientists, for the same reasons.

Although Alsheimer and I have observed differing deer responses to artificial signposts, we agree that deer of both sexes and all ages are readily attracted to man-made signposts.
That said, here’s my take on the subject of buck antler rubbing behavior, as determined by using an artificial investigative approach.

Basics

Normally, only antlered bucks make visible buck rubs. However, even antlerless bucks will attempt to make rubs, especially soon after antler casting. Logically, some antler rubs are made to clean the antlers of velvet, but most are made for communicative purposes. Admittedly, even researchers don’t fully understand the messages bucks convey by such behavior.

Researchers assume the primary glandular secretions deposited on rubs come from the buck’s forehead glands, but secretions from the preorbital or nasal glands, or even saliva, might be involved. Whatever these mystical signals are, they identify the maker and convey significant information to other deer.

Rut-experienced mature bucks are more hormonally charged than younger individuals, tend to rub earlier in the season, rub larger-diameter trees and re-rub trees more often. In the absence of mature bucks, yearlings will make about half as many rubs as compared to older individuals.

At high deer density, natural herd sex-age structure and in favorable young forest growth, densities of nearly 4,000 rubs per square mile have been reported. That’s a lot of scarred scent-marked trees.
In a recent article, Alshemier listed five types of rubs. I have no problem with those identified. However, I would include one more: what appears to be a rub-scrape combination.

Maybe I’ve missed it in the popular press, but I’ve not seen anyone mention ground pawing immediately in front of a rub. I’ve never observed a buck make a rub-scrape combination, and such signposts don’t seem to be very common. All those I’ve found involve a conifer sapling.
Because highly aggressive bucks sometimes paw the ground before or after an aggressive confrontation with another buck, I assume such a signpost is a show a dominance — possibly a mock fight — made only by battle-experienced mature bucks.

An Artificial Approach

My experience with fake buck rubs started in the early 1980s, in the square-mile Cusino enclosure where deer sex, age and density were carefully regulated. But it wasn’t until the early 1990s that I expanded my efforts by systematically using selected poles to determine species preferences for antler rubbing, incidence of re-rubbing, seasonal patterns and more. More important, I then used trail cameras set at fake and natural rubs to identify markers and readers.

Despite considerable regional differences in deer behavior, most studies report that bucks prefer to rub smooth-barked trees with small trunks devoid of lower branches. Also, the stem should be of the type that is easily debarked, and when rubbed, the inner cambium of the stem should show a light color. The most attractive stems for rubbing seem to be along forest-opening edges, where deer can see them from a fair distance. Other investigators suggest that deer show preference for rubbing aromatic species.

Considering the evidence, I couldn’t see why the right kind of stem had to be more than 5 or 6 feet tall. After all, some bucks even prefer to rub fence posts. In fact, there seemed no reason why a potentially attractive rubbing stem even had to mimic a real live tree or shrub, as long as it possessed certain properties that made it an attractive and effective signpost.

Testing a Theory

I tested my theory in the Cusino enclosure by using trembling aspen, a common and frequently rubbed species in the North. In September, I cut 25 aspen saplings, each about 2 inches in diameter, from outside the enclosure. I then trimmed away all their branches, leaving poles about 8 feet long. I set them in place along opening edges after coring out 18-inch-deep holes using a 2-foot length of 2-inch diameter pipe. I simply stuck the poles in the holes and tamped the soil firmly to hold them in place.

Phenomenal Results

Buck response to the poles was phenomenal. Twelve of the 25 poles were rubbed the first week. Within two weeks, 23 poles had been rubbed, and many of them showed signs of repeat rubbing. After five weeks, all stems had been rubbed multiple times.

The resultant high frequency of rubbing was unexpected, but the repeated rubbing of the poles was even more surprising. Except for traditional rubs — those of more than 3.5 inches in diameter that are rubbed annually — bucks reportedly only re-rub 5 percent to 10 percent of their established rubs during the same season.

Two weeks into the study, I set a second unrubbed aspen pole beside each of the 23 poles that had already been rubbed. My question was: Which stem would bucks prefer to rub; one that had already been marked or the new one? As you might expect, revisiting bucks selected the unrubbed stem, thereby leading to clumping of rubs. After three weeks, all of the new poles were rubbed, and 21 showed signs of repeated rubbing.

Competitive Signposting

Luckily, I had set up an automatic camera at one such pair of rubs — one rubbed, one not — and documented an interesting sequence of competitive marking by three bucks. I reported the observations in my first article as Deer & Deer Hunting research editor in the June 1994 issue (see “Competitive Signposting” on Page 46).

At that site, on Oct. 11, I set the unrubbed pole about eight feet from the rubbed one and the camera nearby to photo both poles. No deer visited the poles until Oct. 16. Then, three bucks — in increasing order of dominance —rubbed the new pole during a nine-minute period. That is, the lowest ranked individual (1½ years old) rubbed the pole first, and then a 2½-year-old rubbed it, and finally the area’s most dominant buck (9½ years old) rubbed it. It’s interesting that no deer visited the poles during the first five days, three bucks visited the poles during a brief period and then no deer visited for at least two days afterward.

These observations indicate that bucks sometimes compete seriously to establish signposts on preferred stems when few are available at choice locations. Also, even in the presence of mature bucks, young individuals might become involved.

Preferences

After seeing bucks respond so favorably to hand-placed aspen stems, I conducted a brief experiment to determine buck species preference for rubbing. I chose four species that differed in bark toughness and aromatic quality: trembling aspen, black cherry, balsam fir and sugar maple. All poles were cut into pole lengths (2-inch diameter and 8 feet long), trimmed of branches and set (four species per site) at 25 locations. The test ran Sept. 28 until Dec. 2.

Of the four species tested, trembling aspen stems scored the highest. They were most frequently rubbed (100 percent) and re-rubbed (96 percent), and showed the greatest rub length (21 inches). Black cherry rated a respectable second place in all three categories (88 percent rubbed, 77 percent re-rubbed and average rub lengths of 15 inches). Balsam fir and sugar maple were less frequently rubbed (60 percent and 44 percent, respectively), seldom re-rubbed (20 percent and 9 percent, respectively) and had smaller rubs.

Depending on what’s available, other studies show that buck rubbing preferences vary a great deal regionally. Some species favored for rubbing in one area are not in another. Also, some investigators have found bucks prefer to rub aromatic species, provide they are of the proper size, are in the right location and have smooth, easily removed bark. Black cherry, for example, has been reported to be such a favored species. However, when given a choice, bucks in my study favored the non-aromatic aspen over cherry, probably because rubbed aspen was highly visible. Even the fake rubs, which lacked buck forehead scent secretions, readily attracted the attention of bucks, does and fawns.

Visibility versus Odor

Keep in mind, I placed my poles along opening edges, where deer commonly gathered during the evening and at night to socialize and graze, and where resultant rubs were highly visible and most likely to attract attention. It’s possible bucks might show more preference for aromatic species in dense cover, as has been reported by Grant Woods in his studies regarding whitetail establishment of traditional rubs and Alsheimer during his use of artificially placed stems.
(Interestingly, the most heavily used traditional rub in Cusino’s deer enclosure was a heavily tarred utility pole, probably because it was at a heavily used deer crossing.)

It’s only common sense that buck rubs serve to attract the attention of other deer. So the location of buck rubs is extremely important. That means bucks are most likely to make them in areas of high deer activity — such as feeding and bedding areas or along habitual travel lanes — provided good rubbing stems are readily available. Even within a given area, that also means concentrations of rubs might markedly change during autumn and from one year to the next, depending upon environmental factors and herd sex-age structure.

Conclusions
At least in some cases, a scarcity of rubs, increased competition among bucks for favorable stems or tendency for mature bucks to heavily use traditional rubs might merely reflect a shortage of choice rubbing stems, not necessarily a shortage of bucks. Likewise, stem selection by bucks for rubbing might hinge heavily upon what’s available at choice sites. Given the whitetail’s “plastic behavior,” don’t be surprised if your observations differ from mine.

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