It's the week of November 9th and the woods I hunt are littered with scrapes. Some small, some medium size, but what they lack in diameter, they make up in consistency. You see, every scrape is somewhere along a main trail, typically near an intersection of two trails, every scrape has the broken twig directly above it, and every scrape is set upwind of the buck trail. But this article will not go into how to set up on a scrape. This first feature in our latest column "The Armchair Biologist" will talk about the science behind scrapes. Why bucks do it, what physiological functions come into play, and how they work within the social structure of the whitetail herd.
First: The Tools
Overhanging Limb - 3.3 - 6.6 feet above the ground. The buck will typically hook this with his antler, often standing up on his hind legs to reach it. He will mouth it and pull the limb down, he releases the branch, letting it snap back across his glandular forehead. Often the buck then breaks or twists it - causing it to hang down above the scrape.
Deer Trail - A buck will rarely make a scrape away from a main deer trail. Typically the scrapes can be found where two trails intersect or in a funnel area. Mind you, a mature buck usually has his own trail which is downwind of, and parallel to, the main trail used by does and immature bucks.
Moist Soil - in dry, sandy conditions as those found in the Southwest and the Texas brush country, bucks will seek out darker, more secluded areas of a main deer trail to make a scrape. Moist soil seems to be a requirement of a buck unless there is none to be found.
Second: The Technique
Working the Limb - The buck will seek out the right location along a main deer trail. Once he finds the overhanging branch, he hooks the branch and lets it rub along the frontal gland located in the forehead. The buck will often lick the branch and continue rubbing it a few times before, during or after he paws away the earth.
Pawing the ground - He will then proceed to paw away leaves and debris, exposing the moist dark earth with his front legs and occasionally his back legs. Once the spot is sufficiently cleaned of leaves and other debris, the buck steps forward until his two back legs are roughly centered into the scrape, puts his hooves together, arches his back and pees on his tarsal glands which are located inside the back legs. This technique is often called "scenting," or "rub urination." This ritual does not produce an intense stream of urine, but rather a trickling down the legs where the urine, mixed with the Tarsal scent, runs down the deer's legs and into the fresh earth where it leaves an odor. Rarely do bucks defecate on the scrape but I have seen it on a few occassions.
Here is the characteristic pose of the whitetail urinating on his hock glands
Timing - The timing of scrapes is directly related to the breeding cycle and the "state" of the buck. As the days grow shorter in late October and through November, the buck begins making scrapes, sometimes up to a hundred in a square mile area. As the does become receptive, scrapes begin to look old and unused.
Fourth: Theories of why deer make scrapes
Advertising his sexual services - While nobody knows with certainty the reasons bucks create scrapes, it is a widely held belief that bucks use scrapes to "cold call" for receptive does. By leaving his scent and his mark on the ground, the hope is that a receptive doe will find it, then hang around the general area for him to return and breed her.
Data Profile of the Deer - Recent theories look for a more territorial explanation for scrapes rather than the common "calling card" one. Many biologists now believe that the scrape is more of a data profile of the buck. Telling clues about his health, his sexual readiness, and his dominance or lack thereof in the social structure of the deer herd. This is believed to be true since not all mature bucks leave scrapes during the rut, and there is growing evidence that alpha does create them as well - a behavior not limited to the breeding season.
Territory and Dominance - The final theory for scrapes is that bucks leave these signposts as a threat to other bucks - "this is my turf." This helps to suppress bucks both within the local deer herd, and meandering bucks that an area is off limits. Like posted signs - they keep out those who are not brave, or stupid enough to defy them.
*Data Graph by (Kile and Marchinton, 1977)
*Drawn deer graphics - (Moore and Marchinton, 1974)