At a time when technology finds a home just about everywhere, even in hunting, a white-tailed deer's hearing may be its last defense against "high tech." Hunters today can buy camouflage clothing specially engineered to evade a deer's eyes, and scent-blocking soaps, sprays and undergarments to foil its nose. But gear manufacturers have never devised a way to neutralize deer hearing. To keep from being heard by the herd, modern hunters still just have to know how to keep quiet.
Depending on conditions in the deer woods, keeping quiet is not always possible. Hunters can't move through the woods without walking, and if it's dry and the wind is still, footsteps in fallen leaves and cracking twigs sound a loud alarm. Scientists who study deer senses for other reasons, such as to develop deer deterrents along highways, say a hunter's best means of remaining unheard is to know how deer behave in the woods, be observant and adapt hunting style to conditions. Observant hunters can even use the way deer hear to their own advantage.
"Research seems to indicate that a deer's hearing is really not much more acute than ours," said Karl Miller, professor of wildlife management at the University of Georgia. "They are not like the 'Six Million Dollar Man' who could hear the bad guys whispering at a quarter mile. Instead, a deer knows you're in the woods simply because you are making some noises that aren't supposed to be there."
Miller described a series of studies that determined deer hear sounds in approximately the same auditory range as humans, but with slightly better acuity at high frequencies. A team at Texas A&M University identified deer responses in a frequency range of 0.5 to 12 Khz, with greatest sensitivity at 4 Khz, which matches the range of recorded deer vocalizations, such as grunts and bleats.
Instead of developing super-sensitive hearing, as it did with its sense of smell, the white-tailed deer keeps track of sounds in its sound environment by awareness of its surroundings and "funneling" sounds with its large movable ears, known to scientists as "pinnae."
"The large external ears work somewhat like a satellite dish," Miller said. "They help to amplify sound, but because they can move independently of each other they also help the deer evaluate what is happening in all directions."
Hunters, Miller said, can take clues from deer by watching the ears.
"When traveling together, deer keep track of one another by listening. So, if you see a lone deer, watch its ears. If it frequently cups one or both ears to the rear, you have a good bet that there is another deer following," he explained.
The posture of the ears can also be a sign as to whether a deer has the hunter pinpointed, and is ready to bolt.
"If a deer is looking directly at you, don't be too concerned if its ears are moving in different directions," Miller said. "However, if it has both ears cupped toward you, you've been spotted and he's trying to get all the information he can."
The kinds of sounds a hunter makes are at least as important to stealth and hunting success as the sounds' volume. Deer are accustomed to hearing squirrels running through the leaves and limbs falling from trees. It's the "unnaturalness" of noises that clues deer into a hunter's presence.
"Deer live in the woods 24 hours a day, seven days a week. It's their home. They know what sounds are normal there, and what sounds are not," Miller said. "The unnatural cadence of a human's walk or the 'ting' of metal-on-metal is instantly identified as foreign and raises suspicion."
Hunters can minimize their disturbance in noise-generating conditions -- brittle leaves, crunchy snow -- by walking in an erratic, stop-and-go pattern. But the most effective approach is simply to "go with the flow" and adapt.
Don Meredith, who hunts white-tailed deer and writes about it in Alberta, Canada, advises hunters to save their stalking attempts for times when the woods are quiet -- wet leaves, powdery snow.
"It's been a tough few weeks on the deer hunting trail here. The weather has been unusually warm and there has been very little precipitation," Meredith said. "The best strategy for [noisy] kinds of conditions is to set up on the ground or in a tree stand and wait for the deer to come to you."
First Published November 29, 2009 5:00 AM