Signpost Secrets II: Revealing the Mysteries of Whitetail Scrapes

mockscrapeAs I discussed in my previous “Whitetail Behavior” blog, white-tailed deer rely heavily on scent-marking at antler rubs and scrapes, commonly referred to as signposts, to communicate information of social significance, especially during the breeding season. There’s good evidence deer can communicate individual identity, dominance rank, physical condition, breeding status and other bits of evidence through glandular secretion and urine deposited at rubs and scrapes.

By John J. Ozoga, Deer & Deer Hunting contributor

Compared to antler rubs, however, whitetail communication via scrapes is more complicated. It’s also a subject that has been elaborately abused and fictitiously presented by outdoor writers and the deer scent industry for hunting purposes.

If you follow popular literature concerning whitetail scraping behavior, you’ll find mention of boundary scrapes, territorial scrapes, community scrapes, communal scrapes, hub scrapes, primary scrapes, secondary scrapes, breeding scrapes, travel-lane scrapes and more. Of course, writers seldom agree on the terms between themselves. And I seriously doubt such an elaborate array of scrape terminology is warranted.

Although we don’t fully understand many aspects of whitetail signpost communication, it’s my contention much can be learned by applying an artificial study approach, as demonstrated in the previous fake rub article.

Here is my experience using mock scrapes as a means of determining when, where and why scrapes are made — and who is responsible.

The Scrape

When trying to unravel the mysteries of whitetail scraping behavior, I believe it’s essential to stick to basics. Don’t make the subject more complicated than it really is. Carefully consider the anatomy of a scrape and the physiological reasons behind scrape behavior before trying to psychoanalyze every bit of pawed turf you find. Recognize, for example, that the full scrape sequence involves scent-marking overhead limbs, pawing the ground and urinating into the pawed area. Further, these behaviors might occur independently of each other year-round.

Odor communication in deer at scrapes might involve urine, saliva, vaginal secretions, specialized skin glands and probably some other things we don’t fully understand.

Secretions deposited on overhead limbs at scrapes could come from the forehead gland, preorbital gland, nasal gland or possibly saliva. Secretions in the pawed soil likely come from urine and the interdigital, metatarsal or tarsal glands.

Also, remember that a buck’s scraping ability is determined by his physical, physiological and behavioral maturity. It’s also affected by his reproductive condition, dominance status and probably other factors we don’t know much about. Invariably, mature bucks do the best job of scraping.

If you read my previous article concerning fake rubs, you’ll remember that compared to mature bucks, yearling (1½ years old) bucks commence rubbing later in the season and usually rub smaller stems but still make roughly one-half as many rubs as older bucks. When it comes to scraping behavior, yearling bucks demonstrate even less polished skills. In the absence of mature bucks, yearlings only make about 15 percent as many scrapes. Therefore, you’ll find little serious scraping activity in deer populations harboring few mature bucks.

An Artificial Study Approach

Despite the seemingly complex nature of scraping behavior, in the mid-1980s, I concluded the most important feature of an active scrape was the overhead limb. Because a well-used scrape can be eliminated by removing the overhead limb, I theorized the opposite was also true. That is, bucks should also be induced to scrape simply by providing a properly positioned overhead limb in a favorable location.

In 1987, I set up a study within the Cusino square-mile deer enclosure to determine if white-tailed deer would make scrapes beneath human-positioned limbs. At the time, the enclosed deer population consisted of nine adult males, 26 adult females and 21 fawns.

In August, I selected 20 areas along deer trails with open understory vegetation that appeared favorable for scraping but lacked suitable overhead limbs. Two sugar maple saplings — trimmed of leaves and lateral branches — were nailed (using aluminum nails) to separate trees about 30 feet apart at each area and left in an upright position so the terminal ends were out of reach of deer. The stems varied from 4 to 8 feet long, but each was relatively slender and bowed slightly downward when suspended over the trails

On Oct. 8, the saplings were fastened so the terminal end of each centered about five feet over a deer trail. I cleared away litter from beneath one limb of each pair to expose a circular area of soil. Thus, deer were offered the overhead limb at one site and an overhead limb and exposed soil at the other.

Bucks converted 24 of the 40 artificial sites (60 percent) into scrapes from Oct. 8 through Nov. 12.

They did not show preference for those with exposed soil, in terms of the proportion of test sites pawed or the frequency with which they repawed them.

That experiment demonstrated that bucks could easily be induced to scent-mark limbs and scrape where I wanted. Exposing the soil wasn’t necessary. All that was necessary was to place the proper type of overhead limb in the right place.

Based on my observations, I concluded that preferred scrape sites were those with concentrated deer activity, an open understory, relatively level ground and moderately dry, easily exposed soil.
Given my success, I arbitrarily divided the enclosure into 15 compartments of roughly equal size.

Within each compartment, I selected one to four favorable looking scrape sites that lacked overhead limbs. In all, I selected 50 sites. I then set up two sugar maple saplings about 30 feet apart at each site for future deer scraping behavior study.

These 100 limbs, distributed throughout the enclosure, served as my experimental sites the next five years. The advantage of my scheme, of course, was that I not only had established areas to inspect for pawing, but I had a large number of specific limb tips available to test various controlled scenarios and examine for scent-marking.

Without going into a lot of detail, here are some of things I learned about whitetail scraping behavior by using a highly artificial but scientific study approach.

Year-Round Signposting

Although whitetails make most (if not all) antler rubs during their hard antler phase, certain aspects of scent-marking at scrapes probably occur year-round.

My studies found that deer readily scent-mark at scrapes from May through November, but that the type and intensity of marking varies seasonally. The most frequent scent-marking occurred in May and June and October and November, but the seasonal pattern of scent-marking, limb mutilation and ground pawing at scrape sites varied.

Based on breakage of the limbs or the presence of hair on the limb tips, I found that 94 percent of the test limbs were scent-marked by deer. Although deer occasionally ground-pawed during the spring-summer period, most such behavior did not intensify until autumn; 60 percent of the limbs were scent-marked before serious ground-pawing started.

It’s interesting that I detected no serious limb-tip mutilation until October, at the same time bucks initiated serious ground-pawing. During summer (non-reproductive months), deer marked overhead limbs quite gently, giving heavily used limb tips an oily or greased appearance. They treated the limbs more roughly during autumn (reproductive period), chewing the limb tips or breaking them with their antlers. Whether they urinated at these sites is not clear.

Pawed Turf

Therefore, the manner in which deer scent-mark limb tips above scrapes changes seasonally. Because bucks are more inclined to paw, urinate and tarsal-rub at scrape sites in autumn, this also hints that substances deposited and messages conveyed in such marking likely differ throughout the year. Interestingly, 50 percent to 80 percent of the observed full-fledged scrapes occurred annually during September and October, before the first doe bred.

In 1988, I also conducted a study to determine if scent-marking during summer influenced the amount of scrape activity at a particular site during autumn. I did this by lowering one limb at each paired-limb site throughout summer while leaving the companion limb out of deer reach until autumn.

Of those limbs left down for possible summertime scent-marking, 80 percent developed into full-fledged scrapes during autumn, compared to a 62 percent pawing-rate for the up-limbs. Also, deer were more than twice as likely to repaw scrapes beneath the down-limb sites.

None of my 100 test-limb sites were pawed by deer in May or June. However, deer pawed several other sites each spring and summer, indicating the full scrape sequence played a subtle but potentially important role in buck behavior even during the non-breeding period. Camera monitoring at one such site April 30 revealed a 4½-year-old buck standing on his hind legs to mark limbs more than 6 feet high. Also, fresh urine could be seen in the pawed site. About three hours later, a 2½-year-old buck inspected the site.

This suggests that some prior (summertime) scent-marking at potential scrape sites increased their autumn use. However, not all limbs marked during summer developed into scrapes in autumn. Likewise, 75 percent of those limbs that did not show obvious scent-marking during summer also became active scrapes in autumn.

Message Senders and Readers

From May 1991 through February 1992, I used trail cameras to photograph deer using scrapes. I used various protocols, including random sampling of the 100 test sites and at natural scrape sites, in an attempt to identify the message senders and readers.

Results from these photographic studies confirmed my suspicions. Namely, the primary markers and readers involved in limb-marking are bucks. Of 76 deer photographed marking or inspecting overhead limbs, 86 percent were bucks, 6 percent were adult does and 8 percent were fawns, despite a herd comprised of roughly 30 percent bucks, 30 percent does and 40 percent fawns.

By comparison, I photographed 89 deer at ground level in or near active scrapes during October and November. Of those photographed, 26 percent were bucks, 13 percent were adult does and 61 percent were fawns.

Bucks were photographed smelling the limb tip, some had their antlers or forehead up to the limb, and others were obviously mouthing the tip or moving it along their snout. Most of the scent-marking appeared to be by bucks 3½ years or older, especially during the breeding season. But even younger bucks marked limbs during summer.

Of 16 adult bucks in the enclosure during this series of tests, all but two were identified in photographs at limb tips overhanging active scrapes. Five bucks were photographed at one limb, and seven were recorded at another.

In other words, all deer were attracted to scrapes, but does and especially fawns paid more attention to olfactory messages deposited through urine than to glandular secretions left on overhead limbs. However, bucks were more highly attracted to limbs above scrapes.

Scent Application

As mentioned, mimicked ground-pawing beneath artificially positioned overhead limbs did not increase deer scraping activity. So, I went further in a series of tests to determine if pawing plus application of a commercial doe-in-heat scent or buck urine enhanced their use by bucks.

Using 20 pairs of my artificially positioned limbs, beginning in early October, I applied a doe-in-heat lure beneath one limb of each pair three times a week during a three-week period. The companion limb received no special treatment. I compared weekly pawing rates beneath the treated and untreated limbs through mid-November, which covered the most active scraping period in northern Michigan.

During the test, bucks pawed 14 treated sites and 14 untreated sites. Six treated sites and seven untreated sites were repawed one or more times. In other words, I couldn’t prove that treating the scrapes made them more or less attractive.

Response to Buck Urine

In 1988, I initiated a four-year study to evaluate the effects of buck rut urine applied to mock scrapes. My objective was to determine if I could advance the rutting behavior of bucks and, in turn, trigger earlier-than-normal breeding behavior among enclosure does.

During alternate years, I made mock scrapes beneath one limb of each pair, complete with mimicked pawing and about 2 ounces of urine collected from a prime-age buck during the rut. During treatment years, I serviced the 50 mock scrapes daily from Sept. 5 to Oct. 6, but only freshly pawed the mock scrapes twice a week from then until Nov. 7.

Deer response to the treated mock scrapes was impressive, to say the least. More than 90 percent of the treated mock scrapes were visited by deer during the first week after construction. Overall, the deer visitation rate in September was about double of that in earlier studies when I only tilled the soil beneath artificially positioned limbs.

Seasonal scraping patterns during the non-treatment years (1988 and 1990) were similar to patterns recorded previously. In 1988, the first scrape appeared Sept. 26, and in 1990, the first scrape was made Oct. 2. As expected, peak scraping during the control (non-treatment) years occurred the last week of October and the first week of November, when more than 50 percent of the season’s total scraping occurred.

In 1989 (the first treatment year), the first scrape was made Sept. 6, less than 24 hours after I started mock scraping and adding buck urine. It escalated rapidly thereafter. I recorded 32 scrapes by Sept. 26, compared to only one during the same period the previous (non-treatment) year. Although buck response was not so dramatic the second treatment year (1991), bucks commenced scraping earlier (Sept. 9) than normal. Also, regardless of treatment, annual scraping activity peaked during the last week of October and first week of November.

Interestingly, bucks readily pawed my mock scrapes but were twice as likely to repaw scrapes they initiated. In 1989, for example, bucks pawed 39 of 50 mock scrapes, but only six were repawed three or more times. By comparison, bucks converted 40 of 50 paired (untreated) limb sites into scrapes, 14 of which were they reopened three or more times.

For whatever reason, four mature enclosure bucks died from fighting injuries during this four-year study, and another died the next year. To my knowledge, no enclosure bucks died from fighting injuries during the previous 24 years. This leads me to believe my mock scrapes with urine from a foreign buck were at least partly to blame for the resultant social disruption.

Although application of buck urine to mock scrapes in early September induced earlier-than-normal scraping activity among enclosure bucks, the breeding dates of does weren’t affected. Regardless of treatment, the first enclosure doe bred each year during the first week of November, and some didn’t breed until December. In other words, earlier rutting behavior by bucks did not trigger early estrus in does.

Conclusions

The more we learn about whitetail signposting behavior, the more we realize how poorly understood it is. Although ground-pawing associated with scraping tends to be a seasonal phenomenon, some aspects of scraping behavior — such as limb scent-marking — apparently occur year-round. So the exact chemistry involved and the messages conveyed seem to change with the season.

Full-fledged scraping ability — complete with urination, ground-pawing and limb scent-marking — improves with buck age. So an abundance of scrapes immediately before peak whitetail breeding activity is a good indicator that mature bucks are around. But even mature bucks might vary in their scraping intensity, and the frequency with which they revisit their scrapes is seldom predictable.

Despite all the uncertainty, my studies demonstrate that mock scrapes really attract deer. You can make them as simple or complex as you wish. Often, it might require little more than placing a good overhead limb in the right place and letting bucks do the rest.

Logically, scraping away the duff and doctoring mock scrapes with lures such as deer urine or certain glandular secretions might increase buck visitation rates, but I can’t prove it.

Live the deer hunting lifestyle year-round!

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