American Hunter - October 2019 - 39

Photo: Grace Bartlett / ChuckAndGraceBartlett.com

Deer vs. Human Ears
In fact, a deer's actual hearing abilities
aren't all that much better than the average human. Researchers at the University
of Georgia in 2006 conducted "auditory
brainstem testing" in hopes of learning the
whitetail's minimum hearing capabilities.
These tests involved immobilizing deer
with drugs, placing electrodes on their
heads and monitoring results on computer screens to analyze how a deer's brain
responds to various sound frequencies.

specific sounds played through headphones. To better assess the whitetail's
actual hearing range, researchers must
somehow train deer to give reliable
"behavioral" responses when they hear
various sounds at different levels.
A research team in Ohio-audiologists Henry E. Heffner and his son Henry
Heffner Jr.-devised a solution in 2010
by training two captive female deer at
their farm to drink from a metal bowl.
They wired the bowl to mildly shock the
deer after "warning" them with sounds
of various frequencies and decibel levels.
The shock wasn't strong enough to
make the deer avoid the bowl. The deer
learned they could drink until hearing
the sound. The deer then broke contact
with the bowl, and resumed drinking
when the sound quit.
The Heffners' painstaking tests eventually pinpointed the whitetail's hearing
range from .115 kHz to 54 kHz. Further,
by increasing the sound's intensity to
over 90 decibels, they learned the deer's
hearing range reached 64 kHz. The
Heffners' conclusion: Deer have better
high-frequency hearing than do humans,
but worse low-frequency hearing.
The study's lead researcher, Gino
D'Angelo, and his team learned a deer's
hearing range extends from .25 kilohertz to
30 kHz, but it hears best in the 4 to 8 kHz
range, which overlaps the primary sound
range of the whitetail's vocal communications. Specifically, of 12 identified whitetail
vocalizations in previous research, most
had frequencies of 1 to 8 kHz.
Those frequencies differ little from
human hearing, which is best between 2
and 5 kHz, with an upper range of about
20 kHz. Still, the UGA researchers noted
that deer can detect higher noise frequencies than humans, but pinpointing
that exact high-frequency range required
further research they couldn't conduct.
Brainstem tests are limited by science's ability to detect physiological
responses. In other words, those tests
can't account for how deer interpret
information they detect with their other
senses. Assessing those capabilities
requires behavioral research, which isn't
easy when studying wild animals.
It's less trouble to study human hearing, because people can press buttons or
raise fingers to indicate when they hear

americanhunter.org [

39 [ october 2019

Similar Hearing, Different Ears
Dr. Karl Miller, D'Angelo's adviser during
his 2006 research at UGA, said the
bottom line of both studies shows that a
deer's hearing capability resembles ours.
"The hearing-range curves on audiology charts are almost identical," Miller
said. "They're just shifted about 10
kHz. Deer likely hear higher-frequency
sounds better than we do, and we might
hear the lower frequencies better than
they can, but there's more to it than that.
Most humans taking hearing tests are at
least 40 to 50 years old, and some of us
can't hear those higher frequencies anymore. The deer in the Heffners' tests
were 1 and 2 years old. Deer don't live
long enough to lose their high-frequency
hearing. So it's still hard to make foolproof comparisons."
Even so, how can deer use "humanlike" hearing to duck lightning-fast
arrows, detect whiskers rubbing collars
and pinpoint calling or rattling sites deep
in a forest or a half-mile away across an
alfalfa field?
One distinct advantage deer have:
large, maneuverable ears that can

Photo: Donald M. Jones / DonaldMJonescom

N

o whitetail that hears a bowstring's slap at close range
pauses to weigh its options.
And no deer that hears
a coat sleeve catching on
overhead bark seeks second
opinions.
In the first case, the deer instinctively
drops low and springs into flight, sometimes never looking back to see what
scared it.
In the second case, the deer typically
snaps to attention, its ears swiveling and
triangulating while its eyes and nose
probe for answers.
Unless you're hunting with a firearm
and it's already shouldered, you'll likely
have to concede the contest or risk a
running shot. When deer hear unnatural noises inside their innermost security
boundaries, they instinctively flee or
snap to full alert. If they don't interpret
the noise as pending danger, it might be
the last threat they ever take lightly.
Likewise, hunters shouldn't discount
the deer's ears, even though most of us
rank this defense No. 3 behind its nose
and eyes. Yes, deer must be downwind
of danger for their hypersensitive nose
to detect the threat. And yes, deer have
a 60-degree cone of vulnerability behind
them when their side-mounted eyes
look forward. But sounds can be altered,
slowed, accelerated, suppressed or amplified by several environmental factors.
Those influences on noise include
wind, humidity, air temperature, vegetation, ground cover, overhead foliage and
which way the deer's radar-dish ears are
pointed at any given moment. Therefore, even though deer ears can monitor
their entire 360-degree surroundings, this
defensive shield has variables and vulnerabilities that often require translation or
confirmation from the deer's other senses.


http://www.ChuckAndGraceBartlett.com http://www.americanhunter.org

American Hunter - October 2019

Table of Contents for the Digital Edition of American Hunter - October 2019

Contents
American Hunter - October 2019 - Cover1
American Hunter - October 2019 - Cover2
American Hunter - October 2019 - 1
American Hunter - October 2019 - Contents
American Hunter - October 2019 - 3
American Hunter - October 2019 - 4
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