THE MOON'S IMPACT ON THE WHITETAIL RUT
BY CHARLES J. ALSHEIMER
For the last eight years, Vermont wildlife biologist Wayne Laroche and I have
been researching the influence the moon has on the timing of the whitetail rut
in the North. In its ninth year, the project is expected to run for fifteen years.
Why so long, you ask? There are a number of reasons, but the primary factor is
the fluctuation in the timing of the rutting moon (the second full moon after
the autumnal equinox).
who have followed our work (through Deer and Deer Hunting magazine, and
my book Hunting Whitetails By The Moon) know that the timing of the rutting
moon comes within a day or two of repeating itself every eleven years and reasonably
close to repeating itself every three to four years. Consequently, it's important
to collect good data over an extended period of time in order to evaluate the
moon's impact on white-tailed deer rutting activity.
of the Work
been collecting data for the last eight years, our interest in this project was
born well over a decade ago.
Laroche is a respected fish biologist. He's also an avid whitetail hunter who
spends the entire deer season in northern Maine chasing big woods bucks. He became
interested in the moon's influence on whitetails after researching the impact
the moon has on Grouper fish in the Caribbean and the Gulf of Mexico. Afterwards,
as he hunted the Maine woods every year, he noticed distinct fluctuations in whitetail
activity patterns. After studying the yearly changes he began to wonder if the
moon was affecting the way whitetails behaved during November, just as it had
influenced the fish he had studied years before.
interest in lunar-related behavior began in the late 1980s while hunting and photographing.
Up until then I had bought into the research data that originated in the 1950s
and 60s that said the peak breeding period for whitetails in my region of the
North (42nd latitude) would be November 15-20 each year.
a ten-year period (1985-95) I had the opportunity to photograph whitetails extensively
on a large property in the Adirondack Mountains of New York. During this time
I shot hundreds of rolls of film and kept detailed notes on deer behavior. Despite
the deer population and adult-doe-to-buck ratio remaining the same, the peak breeding
period was seldom the same from year to year. Some years the breeding took place
in early November, some years late November, and other years mid-November. It
was obvious to me that something more than photoperiod, or shortening day length,
was driving the timing of the rut's breeding phase.
In the early 90s I became aware of work Laroche was doing that dealt with the
relationship between the width of a whitetail's track and its body size. To learn
more I interviewed him for a magazine article I was doing. We shared many things
about ourselves and our love for whitetail hunting. During the course of our discussion
we talked about the variations we were seeing in the timing of whitetail rutting
behavior. I'll never forget Wayne's comment that he believed the moon was responsible
for the fluctuations in deer activity that we were observing during November.
After our discussion we decided to see if the moon had anything to do with the
timing of the whitetail rut.
To provide further
background and help you better understand the project, I'll offer the hypothesis
for our research.
point in autumn, the amount of sunlight decreases enough to reset the whitetail's
reproductive clock, thus placing the breeding season in November, December and
January in the Northern Hemisphere. Once a doe's reproductive cycle is reset by
a specific amount of daylight, her estrous cycle is ready to be cued by moonlight,
which provides a bright light stimulus to the pineal gland several nights in a
row each lunar month. Then, the rapid decrease in lunar brightness during the
moon's third quarter triggers hormonal production by the pineal gland. Physiological
changes prompted by the pineal gland culminate in ovulation and estrus.
A Northern doe's estrogen level peaks around November 1 as does a buck's sperm
count. With both sexes poised to breed, it stands to reason a mechanism must be
in place if the doe is to enter estrus and be bred under the darker phases of
the moon, which are the third through first quarters. That mechanism in the North
(north of about the 35th latitude) is usually the second full moon after the autumnal
equinox, which I call the rutting moon.
We Know at Halftime
passing year we've added more and more data collection devices to the research
project. In the beginning we only had six adult does to monitor. We now have upwards
of 100 live does from which data for the project can be drawn.
also monitor air temperature, weather patterns and moonlight intensity throughout
the fall. In addition we have twelve Model 500 Trail Timers to record deer activity
throughout each day. Four of the timers are in my farm's 35-acre research facility
and, at any one time, up to eight are positioned in other areas of the property
to monitor the wild, free-ranging deer population. The data, which is collected
from October through December, is downloaded to our computers for analysis.
eight years ago, when no one else was helping us, we now have several serious
whitetail breeders, deer hunters and outfitters across North America (who are
in the woods every day during the fall) keeping detailed journals to chronicle
deer behavior in their regions of the country. This added information has allowed
us to better understand what is happening in other parts of North America during
October, November and December.
We've observed that the second full moon after the autumnal equinox stimulates
both buck and doe rutting activity. After 1999 we made a concerted effort to step
up our data collection, primarily because of the way the rutting moon was going
to fall in 2000, 2001 and 2002. In 2000 and 2001, the rutting behavior was classic
- just as predicted. However, it occurred at different times. In 2000, the rutting
moon was November 11th and in 2001 it fell on November 1st.
In all reporting locales but one, the seeking phase of the rut kicked in just
as expected in 2000, around the 8th of November. The high point of 2000's breeding
activity took place the latter part of November.
In 2001 things were again on target, but earlier than in 2000. The rutting moon
was November 1st, and where the air temperature was less than 45 degrees Fahrenheit
during the day, chasing was reported to be intense by everyone collecting data.
By November 10th it was obvious that the breeding was full blown, and by November
20th most of the primary breeding was over. So, because of the volume of data
collected, the past two years have provided great examples of what can be expected
in the future.
The project has revealed several factors that can greatly
effect deer activity during daylight hours.
As reported last year, the temperature readings and Trail Timer data have shown
us that when the daytime temperature rises above 45 degrees Fahrenheit, deer activity
comes to a screeching halt. With their heavy fur coat and inability to ventilate
as humans do, deer simply cannot function in warm weather.
Adult-doe-to-antlered-buck ratios greater than three to one also decrease deer
activity. This is primarily due to the fact that does are less active than bucks
in November. With far more does than bucks in a population, every available buck
is with a doe when the hot-to-trot rut arrives. On the other hand, in areas where
the adult-doe-to-antlered-buck ratio is one-to-one or two-to-one, buck activity
is greater because there are far less does to go around, resulting in competition
between bucks for breedable does. As one might expect, we also see greater buck
activity in populations that have more mature bucks in the herd.
The impact of human pressure is perhaps the mother of all rut suppressors, especially
when daytime air temperatures climb over 45 degrees Fahrenheit. Going into the
project I had a feeling human presence in the deer woods would affect movement
but I didn't realize the impact would be so great. The Trail Timer data show that
approximately 55 percent of deer movement occurs during daylight hours in areas
where there is little or no human presence. In areas where there is moderate to
heavy human activity, only about 25-30 percent of deer movement is during daylight.
In order to get a better
read on the moon's influence on whitetail rutting behavior Wayne and I have started
to look more closely at how deer move in areas where humans, poor adult-doe-to-antlered-buck
ratios, warm temperatures, and baiting are non-existent or have a minimal impact.
There are few places in the United States where such conditions exist, but northern
Maine is one of them.
deer found in this region are not pressured by man, nature (coyotes and harsh
winters) keeps the adult-doe-to-antlered-buck ratio at less than three to one,
baiting is not allowed, and warm temperatures are not as common as in other regions.
What makes Maine so unique is that it has mature bucks in the population and snow
is often present to tip off serious trackers as to what is going on in the deer
world. So, with few rut-suppressors to contend with, the far northern reaches
of this vacationland are the ultimate place to study the effects of the moon on
As I said
in the beginning of this piece, Laroche spends the entire month of November in
a northern Maine deer camp, living out of an 18'x52' tent. His camp is limited
to eight hunters at a time and each night Laroche debriefs every hunter, asking
them to recall the number of scrapes and rubs observed, the number deer sightings
by sex, the types of activity witnessed, and any other species of animals that
were seen. This data is then analyzed and incorporated into our database. Laroche
and his party cover a remote area of fifty to one hundred square miles on any
is a hunting legend in the state of Maine. He's written two popular books on tracking
white-tailed deer and like Laroche, he and his father spend the entire month of
November in the northern Maine bush tracking the biggest bucks they can find.
At the end of each day they log everything they observe into their journals and
forward this information to Laroche and me. As might be expected, the observations
of Laroche's party and the Berniers have mirrored each other. They also support
the Rut's Three Phases
The whitetail's "hot-to-trot" rut
is made up of three phases-seeking, chasing and breeding. Each blends into the
phase that follows. In fine-tuned herds, where there are a good number of mature
bucks and an adult-doe-to-antlered-buck ratio of three-to-one or less these phases
will encompass about 30 days. In herds where there are too many yearling bucks
and sex ratios are over three-to-one, the rut is almost always drawn out, lasting
as long as 90 days. When the latter occurs, rut intensity usually will be lacking.
With the rutting moon
approaching, maximum levels of testosterone are flowing and bucks begin to feverishly
look for estrous does. A buck's nose dictates when and where he goes, and no doe
group is safe as bucks weave across their expanded territories. At this time,
all the dynamics of buck behavior unite. Bucks are now finely tuned physical specimens
that spend every waking hour rubbing, scraping and looking for does. Judging by
research I've conducted for several years, an active buck might make six to twelve
scrapes per hour during this phase of the rut. The frequency depends on how sexually
active a given buck is.
all the times to hunt, the seeking phase is one of the best, especially for a
peak of this period is usually three to four days before and after the rutting
moon. During this time, bucks are on the move but not yet chasing every doe they
encounter. Their movement patterns through funnels and along scrape and rub lines
are more predictable. Unfortunately, the seeking phase only lasts a short time
before blending into the chase phase.
The chase phase
often gets confused with the seeking phase. The two behavior periods overlap,
but they're different. This phase usually begins three or so days after the rutting
moon and lasts three to four days into the full-blown breeding phase.
the chase phase, does are almost entering estrus, and bucks are frantically trying
to be the first to find them. Now a buck will chase every doe it encounters. Such
meetings often resemble a cutting horse trying to cut a calf out of a herd of
cows. A buck can be persistent, knowing it will eventually find a doe that won't
run. During the chase phase, scraping and rubbing continue, and in many cases
can be intense, especially in a well-tuned herd. The chase phase often brings
more intense fights, especially if two bucks pursue the same doe.
The chase phase can be a great time to hunt, but it often gets frustrating because
the action can take bucks out of range as they chase does.
This is the stage that
gives the rut its name. When a doe finally enters estrus, it will accept a buck's
company wherever it goes. When breeding begins, scraping nearly ceases and bucks
curtail much of the activity that took place throughout the rut's seeking and
phase usually begins about seven days after the rutting moon and lasts approximately
14 days. We've found that 70 to 80 percent of the mature research does will be
bred during this time.
all the rut's phases, the breeding time can be the most difficult to hunt. This
is because does move very little. Consequently, bucks will only move when the
does move. At this time, one of the only ways tree-stand hunters will see action
will be to place their stands in a hot doe's core area or in sites frequented
by doe groups.
The whitetail's rut is an
amazing and complex phenomenon. It's made up of an array of behavioral traits,
each distinctly different but interwoven. Each rut phase works in concert with
the others to ensure the species' survival. After eight years of exhaustive research
it's now apparent that the second full moon after the autumnal equinox is the
rut's triggering mechanism.
better understand how the rutting moon affects the whitetail's breeding season,
check out my book Hunting Whitetails by the Moon in the online store at