March Deer Biology & Behavior -
White-tailed Deer Security Factors
By T.R.
Michels, Trinity Mountain Outdoors
During my
study of white-tailed deer I discovered that deer are affected by
several meteorological conditions that I call Comfort Factors.
Many of these same factors also affect the health of the deer and
can be considered as Security Factors. Deer rely on their sense of
smell, their hearing and their sight to warn them of danger. The
conditions that affect the security of deer include scents, the
amount of light, visibility, and wind speed.
Scents
Scents of
various kinds can be left on the ground or vegetation and in the
air. Pheromones, chemical signals left behind by deer, relay
information to other deer, sometimes hours later. These
pheromones may tell other deer the direction of travel, and the
other deer’s sex, age, social status, sexual readiness, health,
and may impart fear.
Abundant
tarsal and metatarsal scent left behind when deer fight or are in
flight will alert and often alarm other deer, causing them to
avoid the area where the pheromone is left. Abundant interdigital
scent, left when a deer stamps it’s foot after sensing danger,
will alert other deer of possible danger up to an hour later.
Scents of any possible predator; fox, coyote, wolf, dog, mountain
lion, lynx, bobcat, bear or human will alarm deer and cause them
to become alert and avoid the area where the scent is.
Unnatural
scents and those associated with human behavior will cause deer to
become alert and alarmed. This wide range of scents includes
foods, chemicals and medicines from humans, fumes from vehicles,
and the many products humans use in daily life that are not
normally present in high concentrations in areas deer use. The
higher the concentration of the scents the higher the state of
alarm the deer will exhibit.
Two things
cause lower concentrations of scent; dissipation and dispersal.
Because scent molecules evaporate (dissipate) at different rates
(based on the wind speed, temperature and humidity) the longer it
has been from the time the scent was left the less there is, and
consequently the less alarmed the animals are. Scent left in the
air and carried in the wind is spread out (dispersed) by the
action of the wind. The farther scent is blown from it’s source
the less there is, and the less alarmed the animals are.
Sights
Deer depend
to a great extent on their sight to alert them of danger. Their
sight allows them to move at night, and during the low light
conditions of dawn and dusk when they feel most secure. While most
hunters know this they have a hard time translating it into
whitetail terms because we don’t think in terms of light factors,
we think in terms of time of day or hours.
Humans rely
heavily on that piece of technology worn on the wrist called a
watch, but deer don’t have watches or clocks. So, what tells a
deer what time to get up in the evening and begin feeding and what
time to head back to bed in the morning? Deer do have a circadian
clock in their brains. The amount of chemicals in a particular
portion of their brain allows them to know approximately what time
it is. But, although this clock may tell them it is time to move,
the urge to move is overridden by the need for security. And one
of the primary factors that affects the deer’s security is light.
Older deer, bucks in particular, usually wait until the light
factor is right before moving. I don’t know exactly what the light
factor (or lack of light) is that tells deer when it is safe to
move and feed. But, it is definitely low light conditions
resembling the conditions at sundown and sunrise.
Anything
that causes the light factor to resemble twilight or darkness can
cause deer to begin moving. This includes clouds, fog, rain,
sleet, snow and leaves. Yes, leaves. Remember that deer often bed
in heavy timber where the leaves on trees and shrubs provide shade
which makes it darker in wooded areas than it is in open areas.
When there are leaves on the trees deer feel secure in wooded
areas and begin moving and feeding a couple of hours before
sundown. But, they don’t usually move into low brushy areas or
open fields until the light factor there resembles twilight.
Vegetation
Because
leaves have the ability to alter the light factor there is a shift
in deer movement that occurs every fall that most hunters fail to
recognize. Once the leaves fall wooded areas no longer provide as
much shade as they did earlier in the season. Consequently the
deer begin to move in wooded areas and along travel lanes about a
half hour later than they did while the leaves were on the trees.
The hunter who has been watching deer appear at 6:30 along a
wooded trail for a week and then plans to hunt the trail a week or
two later can be in for a big surprise. If the leaves have fallen
the deer probably won’t show up until about 7:00, which may be
after legal hunting hours.
Available Light
As I
mentioned earlier, anything that creates a reduction in the
current light factor, making it resemble twilight conditions, may
cause deer to begin moving earlier in the evening, and staying
later in the morning than normal. These low light factors can
cause bucks to make the mistake that hunters dream of. Clouds,
fog, mist, light rain or light snow often cause deer to move into
open areas up to a half hour earlier in the evening and a half
hour later in the morning than normal, which means they may move
during legal shooting hours. While the light conditions affect all
deer they may be different for individual deer. I have kept a
detailed record of individual deer movement times, including the
subdominant and dominant bucks in my area. The data shows that
bucks in general begin to move later in the evening and leave open
areas earlier in the morning than the does.
Travel Route
Changes
Because
vegetation causes a change in the light factor, leaves, or the
lack of leaves, cause other changes in deer movement patterns. The
travel route of a deer is governed by two major factors, the path
of least resistance and the need for security. Just like humans a
deer doesn’t normally plow through hip deep mud, brush too thick
to get through, or up extremely steep inclines. But, this desire
to travel in the area of least resistance is overridden by the
need for security. Deer normally travel in areas where they are
not easily seen. This security need is also different for each
deer. Bucks wear headgear and are more noticeable than does,
which makes them more susceptible to being killed and eaten by
predators and man. Because of this bucks usually travel, not on
the doe highways, but on their own routes, often paralleling the
doe trails. These buck trails often wind through heavy cover in
gullies, creek bottoms, overgrown roads, or where they area out of
sight of the top or bottom of the hill.
Early in the
year when leaves are still on brush and trees the deer feel secure
moving in vegetation paralleling open areas. But, once the leaves
fall deer can easily see the open area and they feel insecure.
This causes them to move farther into cover. After the leaves fall
deer often move later than they did when the leaves were on the
trees. This really hit home with me while hunting a trail that
paralleled a road. Early in the season the deer used a trail about
seventy-five yards from the road. During the week the leaves fell
the deer moved to a trail twenty yards from the road, farther into
the woods. I couldn’t understand why the deer stopped using the
original trail until I got down from my stand and stood on the
first trail where I could see the cars driving past. When I stood
on the second trail I could no longer see the cars. With the
leaves gone the deer felt more secure on the second trail, which
was farther into the woods.
Wind
Strong winds
can carry scents to a deer and cause alarm. Strong winds can also
cause scent to bounce of trees in thick woods, making it difficult
for deer to determine which direction the scent came from. In
either case strong winds make deer uneasy and hard to hunt. Winds
between 10 and 15 miles per hour cause deer to seek shelter in
areas with less wind. They stay in low areas, heavy cover or the
downwind sides of hills and woods, where they can smell and
determine scent direction better while moving and feeding. They
may not leave their bedding areas during high winds With their
large rotating ears deer hear better than humans, and they
probably hear every sound around them. But, when high winds rattle
tree branches and leaves it makes it difficult for deer to
distinguish one sound from another, and they become nervous. The
point is that a deer’s survivability depends on it’s ability to
smell and hear. When high winds make it difficult for deer to hear
or smell properly they do not move far from secure areas. When
they do move it is usually in areas where there is less wind and
less noise.
Thermal
Currents
Thermals,
air currents that move up and down the contours of the land,
affect deer movement because they also carry scent. Thermal
currents usually move uphill as the temperature warms during the
morning and move downhill as temperatures fall during the evening.
Deer take advantage of this by bedding on hillsides during the day
where they catch scents on the uphill currents. When the deer
begin to move toward feeding areas in the late afternoon they
often move downhill, which allows them to detect scent on the
currents that are still moving uphill. During the night deer often
bed in low areas where they can detect any scents on downhill
thermals currents. As the deer move uphill toward their daytime
bedding areas at sunrise they detect scents on the thermals which
are moving downhill.
If you are
interested in more deer hunting tips, or more deer biology and
behavior, click on Trinity
Mountain
Outdoor News and T.R.’s Hunting Tips at
www.TRMichels.com. If you have questions about deer log
on to the T.R.’s Tips message board. To find out when the rut
starts, peaks and ends in your area click on Whitetail Rut Dates
Chart.
This article
is an excerpt from the Deer Addict’s Manual Volume 5 ($9.95 +
$5.00 S&H), by T.R. Michels.
T.R. Michels
is a nationally recognized game researcher/wildlife behaviorist,
outdoor writer and speaker. He is the author of the Whitetail,
Elk, Duck & Goose, and Turkey Addict’s Manuals. His latest
products are the 2003 Revised Edition of the Whitetail Addict’s
Manual, the 2003 Revised Edition of the Elk Addict’s Manual; and
the 2003 Revised Edition of the Duck & Goose Addict’s Manual. For
a catalog of books and other hunting products
contact: T.R.
Michels, Trinity Mountain Outdoors, PO Box 284, Wanamingo, MN
55983, USA. Phone:
507-824-3296, E-mail:
TRMichels@yahoo.com,
Internet
Site:
www.TRMichels.com
