When a deer inhales, it is able to identify and sort a complex array of odors, including those of hunters and cover scents. Photo by Ron Sinfelt.

A good olfactory sense is a deer's best defense. Hunters have known this for thousands of years, but for the last two decades, a revolution led by science has changed the way we hunt deer from coast to coast.

Hunters see only a fraction of the deer around them. Odor lingers long after a hunter has passed. Deer that cross his trail are alerted. The hunter might hear the warning blows or snorts that are the signals that a deer has caught his scent, but by then it is too late.

When a deer inhales, it can identify and sort a complex array of odors. Some are food or herd smells; some are warnings. Deer also communicate by means of scent signals that include pheromones.

Tarsal, metatarsal, preorbital, interdigital, forehead, nasal, preputial and caudal glands secrete scent information. A specialized organ in the roof of the deer's mouth is believed to help a buck determine a doe's timing and may synchronize the reproductive physiology of the buck.

Does can pick out their fawns by scent. Bucks stake out territory and advertise for does during the rut, and the readiness of the doe is activated by scent detection.

Jim Heffelfinger, regional game specialist with the Arizona Game and Fish Department and adjunct professor with the University of Arizona at Tucson, has made a living out of studying ungulates and game birds. In his book, Deer of the Southwest, he described a deer's olfactory attributes. A deer's nasal passages "are lined with a tissue (epithelium) that contains mucus-producing cells. These cells maintain a moist environment in the nasal cavity to aid in the collection of scent. When a deer inhales, it draws in airborne molecules that land on an area of moist nasal lining, and through a chemical reaction, messages are sent to the brain for identification of the scent."

Temperature and humidity also play a role. Cool weather and the increased humidity of autumn improve a deer's sense of smell and make a finely tuned scent detection system even better.

Our challenge in October is to beat a deer's defenses, and we have varying degrees of success based on our implementation of strategy and tactics. We succeed more often when we employ a holistic, no-nonsense approach to scents.

We may never completely control the scent we bring to the woods, but the more we reduce our own odor, the better our odds are of seeing deer.

SCENT ELIMINATORS
Scent can be covered up to some degree, confusing a deer's ability to sort through other odors and detect the human threat, but a better approach is to control human scent before the application of covers and attractants.

Studies have indicated that deer can process up to seven different smells at the same time. That means a deer can smell you as well as the product you trust to cover your scent. By eliminating degrees of human odor, we diminish the scent carried downwind and spread through swirling breezes.

Human scent is carried on clothing and equipment. It emanates from gun oils and fabrics; it is manifested on hatbands and the soles of our feet. Every step we take to block or eliminate scent is a small victory.