Hunting Bucks by the Moon (Part I)

Posted on September 20, 2011

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As reliable as God, who created the lesser light to rule the night!

 

“Try as we have to
disprove the hypothesis that the full moon triggers breeding,

we have not been
able to reject it. We have disproved the hypothesis that moon

position has any real effect on activity.”  Dr. James Kroll

A full moon rising on the eastern
horizon reflecting light from a quickly vanishing sun provides an illuminating
eeriness as its orange glow backlights a naked, statuesque November tree line.
Man, through time has studied, gazed upon with curiosity, romanced, fantasized
and even set his foot down on the surface of this terrestrial sphere. When hung
in an autumn sky, the moon’s looming presence enchants us and casts a warm
spell of mystique to the deer hunter.

What influence, if any, does the
moon have on white-tailed deer activity, particularly their breeding cycle?
Does the moon hold the key to unlocking the mystery of why 70-80% of whitetails
breed on different dates each November? Following an exhaustive thirteen year
study here in the Northeast, where I meticulously monitored both autumn deer
activity and spring fawn births coupled with the collected data from an
on-going, fifteen- year research project conducted by wildlife photographer,
Charles J. Alsheimer and former Vermont Game Commissioner, Wayne Laroche, I’m
convinced that the moon certainly does indeed play a huge role in triggering
the rut. In fact, according to Laroche,

 

“If the moon provides the timing
mechanism for the estrous cycle, what sensory pathway in deer receives the
lunar cue? External stimuli fall into three primary categories: physical,
chemical, and biological. The great distance between earth and the moon rules
out any regular 28-day exchange of sounds, scents or chemical and biological
materials whitetails can detect.

The moon affects the earth’s
gravitational fluctuations and nighttime illumination. Both factors create
external stimuli that deer might detect. However, little evidence suggests deer
or other creatures directly detect gravitational forces.

 

Moonlight can be detected,
especially by whitetails, which have eyes adapted for low-light vision. Light
passing into the eye strikes the nerve-rich area in the back of the eye,
causing electrical impulses to pass along the nervous system to various organs.
Some impulses pass to the pineal gland in the center of the brain, and provide
input to the endocrine system. The pineal gland and related hormones are
involved in or regulate the reproductive cycle. The pineal gland responds to
light by increasing (with diminishing light) or decreasing (with increasing
light) production of a hormone called melatonin. This, in turn, increases or
decreases other hormones.

The fact moonlight changes the
earth’s illumination on a cycle similar to the whitetail’s 28-day estrous
cycle, the fact whitetails have a sensory system that can detect moonlight, and
the fact the whitetail’s endocrine system responds to light stimuli by altering
levels of reproductive hormones argue against coincidence.”

The Autumn Dance

It is Alsheimer/Laroche, and my
belief that the 14-day breeding window, the time frame when 70-80% of the adult
does will enter estrus, begins five to seven days after the second full moon
(rutting moon) following the autumnal equinox (Sept. 23). This scenario holds true
the closer to November 1 the rutting moon falls, intensifying the rut and
facilitating a more predictable breeding timetable. The light of the full moon
is the visual cue that stimulates the bucks and as it waxes over the next 5
days, the darkening nights become the impetus to trigger the doe to begin
ovulating.

On the other hand, in years when
the second full moon after September 23rd falls on or later than November 14th,
the less intense the rut will be, and is commonly referred to as, a trickle
rut. Breeding will begin on the full moon when this scenario presents itself.

To better define the commonly used
word, “rut,” let’s suffice it to mean the actual breeding period and the events
leading up to it. Due to the three overlapping stages involved in this
forty-day process, bucks will exhibit distinct behavioral changes and as the
rut develops it becomes equivalent to a marathon rather than a sprint.

 

Seeking: This sudden
transformation in the buck’s chemistry urges him onto his feet in search of
does. The animal’s nose dictates the direction of his travel. Rubbing and
scraping intensifies and with each doe encountered, the buck will test her
urine by ingesting the scent through the vomeronasal organ located in the roof
of his mouth. This behavior, flehmening, routinely called lip curling,
discloses immediately to the buck if the doe is approaching estrus.

Bucks will begin seeking about a
week prior to the full rutting moon. As the reflective light becomes full, a
buck’s search becomes accelerated and his travels now take him far and wide of
his normal home territory.

Chase: During the process of
seeking, a buck will finally pinpoint a doe near estrus. In his frantic search
to locate and be the initial suitor, he will chase every doe encountered. This
activity usually begins a couple of days following the full moon. Frustration
mounts within the buck fraternity, as trees, shrubs, ground cover, and even
each other become the recipients of brutal attacks.

Tending: Five to seven days
following the full moon does will enter into estrus. When this event begins,
all other rut related activity such as scraping and rubbing ceases with the
buck’s full attention riveted on the act of breeding. This phase will encompass
fourteen days peaking at the halfway point. 70-80% of mature does will be bred
during this period.

Recovery: At the conclusion of the 14-day breeding window and/or
when the sweet scent of estrous no longer hangs in the air, bucks will
literally crash. They will retreat to their bedding area and hole-up for as
long it takes to recuperate, usually between 3-to-5 days.

(Tune in next week for part II
where I will provide my prediction dates for this year’s whitetail rut.)

All images on this site are copyright protected and the property of R.G. Bernier.

© 2011 R.G. Bernier Nature Photography – All rights reserved.

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