ASSESSING 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).

Those 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.

Genesis of the Work
Though we've 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.

My 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.

Over 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.

The Hypothesis
To provide further background and help you better understand the project, I'll offer the hypothesis for our research.

At some 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.

What We Know at Halftime
With each 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.

We 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.

Unlike 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.

Rut Suppressors
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.

The Maine Lab
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.

The 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 deer activity.

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 given day.

Dick Bernier 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 our hypothesis.

Timing 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.

Seeking Phase
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.

Of all the times to hunt, the seeking phase is one of the best, especially for a tree-stand hunter.

The 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
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.

During 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.

Breeding Phase
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 chasing phases.

The breeding 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.

Of 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.

Conclusion
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.

To 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 charliealsheimer.com.

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