For years, hunters have tried to accurately predict the best days
to hunt and which ones would better be spent in bed. Could there be
a scientific method to assure the good days from bad ones? Well, the
answer is yes and it’s called the Deer Activity Index (DAI). What exactly
is a DAI? A DAI is a tool that uses various moon characteristics to
assist hunters and biologists in determining daytime activity levels
When I was young, my grandfather answered all my deer hunting questions.
Although he would never reveal his actual method of analysis, his rationale
for predicting deer movement went something like this; full moons were
good and new moons (dark) were bad. Years went by and I started to
test some of Pap’s wisdom, but, to no avail. All the scrupulous notes
I had so religiously taken simply did not make any sense.
Then in 1991, while working on his dissertation, Grant Woods tried
to determine if the moon had any effect on daytime deer activities.
He worked with various astronomers in an effort to determine what moon
phase or moon position had the best relationship to deer movements.
Through some extensive statistical analysis, Woods dismissed the moon
phase and position components. Why? Because he found that the earth’s
distance from the moon, plus the moon’s declination or degrees the moon
is to the earth’s equator are very different from one full moon to the
next. In other words, all full moons are NOT created equal. The same
rationale also applies to quarter, half or whatever moon phase is present.
Using hunter compiled data in free ranging deer herds, Woods analyzed
information on 6,009 tree stand hours, in which 5,686 deer were seen
and 784 harvested. Other hunts from around the country were also added
to the original sample size and checked with various moon orbit characteristics.
Finally, after a lot of hard work all the statistical comparisons started
to make sense. The end result is called a Deer Activity Index (DAI).
The DAI rates daytime deer activity movements into seven categories
ranging from “4” to “10”. A ten reflects the highest deer activity,
while a “4” indicates the lowest. It is important to note that when
the DAI comes up with a “4”, there still will be deer activity. Although,
it will probably be a slow day afield.
To satisfy any skepticism concerning the statistical analysis, Woods’
research showed that on days with a “8”, “9” or “10” (high DAI) values
at a research site in South Carolina, hunters saw 76 percent more deer
than on “4",“5” or “6” (low DAI) value days. Similar data occurred
at a hunt club in New York. Hunters observed 54 percent more deer on
the high DAI days than on low DAI days.
Similar results occurred for hunters that participate in drives!
When the hunters at the club in New York started to drive deer, the
data indicated 26 percent more deer on high DAI days compared to low
DAI days. Intuitively, one would suspect no measurable or significant
changes with drives, but this was not the case.
I asked Woods his thoughts on hunting during the midday hours while
using the DAI? Woods stated, “I always stay in the woods as long as
my schedule allows when I’m hunting. However, given similar conditions,
I average observing significantly more deer during midday hours on “8”,
“9” and “10” days compared to “4”, “5” and “6” days.”
Although there have been many studies correlating weather conditions
to deer movement patterns, none of them are entirely consist with one
another. Although not significant, barometric pressure seems to be
the only weather parameter that is somewhat consistent with deer movements.
As veteran hunters know, this generally occurs with an onset of a storm.
Woods noticed this occurring during Hurricane Hugo in 1989. On the
day prior to the storm (DAI value “4”), he saw nothing unusual. However,
the day of the storm (which was also rated a “4”), Woods observed deer
feeding under every persimmon tree, even mature bucks. Obviously, extreme
weather conditions can have an influence on the DAI.
you accurately predict when deer are going to move from one day
to the next? Exciting new research can help you predict the good
days from the bad by using a Deer Activity Index (DAI). This hunter
uses his DAI every day and swears by their accuracy! Unlike the
unpredictable weather patterns or food supplies, DAI values are
given to you far in advance.
How is the DAI effected by extreme hunting pressure? Woods' states,
“Unusually high pressure can override the DAI, but under normal hunting
situations deer activities correspond very well.” Can you use the DAI
values to determine the rut? The answer is NO. Findings suggest that
there is no difference between the values when deer actually breed.
In other words, breeding may be just as likely on a “4” day as on a
“10”. If this doesn’t make sense, remember the DAI is for daytime activity
only. On “4” days, breeding can occur, although it most probably occurs
Exceptions do occur, in well managed herds with older age structures
and balanced sex ratios the rut probably out weights any DAI. However,
this is not the case in many parts of the country. As a result, the
DAI is probably a better indicator of total deer movements in areas
that experience a prolonged “trickle” rut.
Why does the DAI work? Some believe it has something to do with the
moon’s gravitation pull. We know that the moon’s gravitational pull
is different every day and the effects are felt through daily high and
low tides. Some argue all living creatures are effected by the moon…just
ask any bartender or police officer. For whatever the reason, the fact
remains that the DAI is the only statistical tool we have to predict
Woods believes, “I can now help hunters and researchers schedule
their field time more efficiently by picking the best days to hunt.
This should be especially helpful for those who have limited opportunities
to hunt.” Testimony to this is reflected by letters sent to him stating,
“By eliminating the least active days, my wife is happier due to the
additional time I was able to spend with her,” or “It was almost as
if the deer had made the activity schedule themselves and mailed it
out to us hunters."
It’s important to note that the DAI does NOT tell you where to hunt,
but a tool that indicates your most probable days for deer activity.
Obviously, hunting know-how is still paramount in being consistently
successful. The bottom line is this, if you have an hour to hunt, then
hunt. But, if you have a DAI then you can modify your limited times
afield to those key “8-10” days.
The DAI may be altered by extremes in weather conditions,
hunting pressure, food availability and/or the rut. However,
Woods believes “normal” environmental factors are generally
not enough to totally override the DAI. Since 1991, the DAI
has been accurate 69-75 percent of the time…not bad! DAI values
are available on a large poster calendar for $12.95 by calling
[888-760-3337] or sending a check or money order to DAI, P.O.
Box 36056, Birmingham, AL 35236-6056 (allow 3-4 weeks for shipping
Winand is a whitetail biologist from Randallstown, MD.
He is a staff writer for Bowhunter as well as Deer and Deer Hunting