Deer are animals of keen senses
White-tailed deer, or any deer for that matter, be they mule or black-tailed deer, elk, moose or caribou, are equipped with amazing senses. These animals' abilities to detect the faintest odors, distinguish the slightest of movements, or hear the tiniest of sounds are the reasons that members of this group of mammals can survive the challenges that life in the wild presents to them every day.
Some of these senses include sight, hearing and touch. Other senses involve chemical stimuli, which engage the senses of smell and taste. Another sense (considered by some research biologists as a sixth sense) is a combination of both taste and smell and is called "vomolfaction." An adult buck utilizes this sense when he simultaneously scents and tastes the urine of a doe as he tests her readiness to breed.
For starters, deer's vision is exceptional, though their ability to identify motionless objects that they cannot verify by using other senses is not as good. But deer's field of view encompasses an incredible 310 degrees -- and they can detect the smallest amount of movement. As well, deer have no problem navigating throughout their environment in broad daylight, complete darkness, and all light conditions in between.
The ability to see in low light and in darkness is the result of a special tissue in the rear of each eye. These reflective tissues, or membranes, "bounces" light coming into the eye across special receptor cells of the retina. This bouncing back of incoming light across receptor cells for a second time effectively brightens images that are dimly lit. This is also the reason why a deer's eyes shine when artificial lights are cast upon them.
Research biologists have also described a protective ring of pigment that encircles the cornea, the part of the eye that allows light passage. This pigment is believed to serve as an anti-glare mechanism that may improve deer's eyesight during daylight hours. And, contrary to long-held beliefs that deer cannot distinguish color, recently published research has confirmed that deer do indeed see some color after all.
During the day deer discriminate colors in the blue to yellow-green range in addition to orange and red wavelengths. At nighttime deer can decipher colors in the blue to blue-green range, but can also detect some colors of longer wavelengths.
Regarding hearing, the next time you see a deer, watch what the animal does with its ears as it stands alert. Deer are constantly swiveling their ears back and forth -- either in unison or independently from each other -- while they listen to and evaluate the sounds that reach their large ears. For example, during an experiment, biologists concluded that one particular black-tailed deer could hear a researcher clicking fingernails behind his back from 75 yards away, upwind, and completely hidden from view.
Not only can deer correctly evaluate where sounds are coming from, they have the remarkable ability to differentiate the unusual or unnatural sounds that occur in their environment from the familiar sounds. Accustomed to the vocalizations and amblings of squirrels and other creatures in the woods, as well as the creaking sounds of trees and rustling leaves in the wind, deer effectively tune out recognizable sounds while listening intently for abnormal sounds. Put another way, if the click of a camera's shutter or the crunch of snow underneath your boots sound familiar to you, it most certainly doesn't to a deer.
Large ears work like megaphones do in amplifying sound. Cupping your own ears with your hands demonstrates this wonderfully. A deer facing away from you will often swivel one or both ears backward to listen. Thus, any sound you make will be amplified into their ear or ears. And that's not all; deer can detect faint and intense sounds alike, but they can also hear frequencies higher than we can.
But perhaps the most important sense to deer is smell, or olfaction. It is undoubtedly why anyone wanting to get close to a deer must take into account both the wind direction and one's own scent. Deer use their sense of smell in a multitude of ways: identifying other deer, determining sexual readiness, locating food and detecting danger. Depending upon the source, I've read that a deer's sense of smell is anywhere from 100 to 10,000 greater than our own.
Glandular secretions, which are produced from four external sets of glands, are important with regard to deer communication. The glands produce scents and are considered to be pheromones. These different scents help deer identify individual deer, and, as expected, are unique to each deer. Tarsal and metatarsal glands are located on the hind legs; the former is involved in individual recognition, whereas the latter communicates alarm or fear.
Preorbital glands (also called tear duct glands), are used when deer, mostly bucks, rub the corners of their eyes onto limbs and brush for marking purposes. Other glands, located between the hooves, are glands called interdigital glands. These "in-between-the-toe" glands help distribute scent to the ground and trails that deer traverse. It's not uncommon to observe a deer walking with its nose to the ground and following the scent-trail of another deer that was laid down by the animal's interdigital glands.
Like olfaction, the sense of taste involves specific molecules binding with receptor molecules in the nose or tongue, in turn causing a reaction. In the case of taste, several rows of taste buds on the tongue enable deer to discriminate between foodstuffs. If an unpalatable food item is tasted, it is dropped, smelled, and likely not tasted again.
Indeed, equipped with such keen senses, it's a wonder we can get close to deer at all. Along with the deer's intelligence and their ability to run and hide, matching wits with white-tailed deer involves getting past their eyes, ears, and noses -- which, of course, is easier said than done as we get out and enjoy the great outdoors.
Blane Klemek is the Bemidji area assistant wildlife manager, DNR Division of Fish & Wildlife. He can be reached at firstname.lastname@example.org