Without the moon, life on Earth might not even be possible. At one quarter the diameter of the Earth and one sixth its gravity, our celestial neighbor plays a critical role in setting marine-life rhythms and moderating the climate of our planet. Scientists have documented its triggering of reproduction periods in corals and marine worms, and how species like horseshoe crabs rely on new and full moons to time their crawl to shore for optimal breeding.
Given such influence, it’s not a big stretch to think that the moon might also affect the movement of animals like whitetail deer, and may therefore be a legitimate factor in successful hunting. Some deer hunters are so convinced of the moon's influence, they'll hardly step foot in the woods without consulting a lunar calendar. And there's plenty of anecdotal evidence, too, of moon-obsessed hunters tagging huge bucks during specific lunar cycles.
But does the moon really affect buck activity? It's a question hunters have been arguing over for ages. Now, thanks to a new study from the Mississippi State University Deer Lab, science seems to have provided an answer. And it's a resounding, Meh.
Traditional Theories About the Moon and Hunting
For as long as hunters have been hunting, we've looked to the moon for guidance. Over time, a handful of theories have taken hold regarding how the moon exactly affects deer activity, some of which are conflicting. Nevertheless, the main factors hunters cite as buck influencers are the moon's phase or brightness in the sky and its position or gravitational influence. The simplest, and possibly oldest moon-phase theory says that buck movement will decrease during a full moon because deer will feed heavily under the bright night sky. This supposedly suppresses movement the next day, as deer are laid up with full stomachs, resulting in poor hunting.
The more complex solunar theory looks at both phase and position, claiming that during new and full moons, buck movement will increase at times when the moon is in a minor window (near the horizon) or in a major window (positioned overhead or underfoot), especially at dawn and dusk. Yet another popular moon theory among hunters, known as the red-moon theory, says that the best times to hunt are during a four-hour window when any phase of the moon is overhead or underfoot in conjunction with a rising or setting sun. With both the solunar and red moon theories, the position of the moon and sun increases gravitational effects and is thought to stir bucks to move early, or keep them out late, giving a slight window of opportunity for hunters to take advantage of.
How Two Experts Factor the Moon Into Hunting Plans
John Eberhart, a well-known hunter author specializing in chasing highly-pressured whitetails, says that the moon plays almost no role in how he hunts, with one key exception. “I’ve found that during the rut, a full moon will hamper night movement of bucks due to fear of exposing themselves in open woods and fields, but substantially increases activity the next day in security cover as they try to make up for lost breeding time.” According to him, a large majority of his mature buck kills have come at midday following a night with a clear sky and full moon in these dense-cover rut locations.
If there is cloud cover, even during a full moon, however, this moon effect is negated, just like during a new moon where there is zero illumination. There is some scientific research that would seem to support Eberhart's theory and oppose the old “don’t hunt the day after a full moon,” adage, especially in heavily hunted areas. A 2013 study on moon luminosity’s effect on nighttime predation risk concluded that there was a suppressive effect of moonlight in more open habitat types across all species. It did not, however, shed any light on buck movement the following day.
Adam Hays III, who has four bucks over 200 inches on his wall, employs a different strategy, primarily planning local and out of state hunts around the red moon. In fact, he attributes so much of his success to the moon’s position that he bought the Moon Guide, a company that produces a lunar table indicating the best times to hunt based on when the red moon falls. Although he also keys in on weather conditions and wind as major factors to time his hunts, he claims that the red moon is a vital trigger for getting mature bucks to move during shooting hours. And though it may seem far-fetched to think gravity can “pull” bucks up out of their beds at certain times, experimental research has attempted to measure the effects of “gravimetric tides,” a field dynamic from the moon, sun, and earth orbits intermingling, and suggests they may have an influence on cyclic behaviors of humans and plants.
These studies are not specific to whitetail deer, however, and hunters, no matter how skilled, can be subject to interpretation bias. After all, if we only hunt under certain conditions, we’re likely attribute any success to those conditions, whether they are causal or not. So how do we really know if the moon in influencing the deer activity we observe or if it’s one of a long list of other complex factors? Probably the best way to answer the moon question is to eliminate all other variables, and crunch much larger data sets than hunters can compile through in-field observations. And that's where the latest study from the Mississippi State University Deer Lab comes in.
What the New MSU Deer Lab Study Shows
In a recently released collared-buck study, the Deer Lab was able to mathematically isolate moon phase data from a 48-buck research project spanning two years. Roughly a million data points were collected by those collars every 15 minutes, which allowed the researchets to get specific answers to two key questions:
How did moon phase and position affect the percentage of time bucks spent bedded?
Did these factors cause bucks to move at a greater rate than usual, thus giving hunters more opportunity?
The striking thing about this analysis was the data allowed researchers to not only account for variables such as weather, the rut, and time of day, but also to track each individual buck and build an average behavior profile for every hour of the day. This in turn allowed them to home in on any moon variable they wanted and compare any deviance from it to that buck’s normal behavior. Finally, they were able to take an average the differences for a broad analysis encompassing the entire population of bucks.
The Results: “Generally speaking, we found nothing," says Deer Lab co-director Dr. Bronson Strickland. "In some instances, we saw an increase in time bedded or in the rate the bucks moved, but in some moon conditions where they were supposed to move more, we actually saw a decrease.” Averages for the moon phases’ effect on time spent bedded in daylight hours was .2% variance from normal, with a 1.1% difference in yards walked per hour. The red moon numbers saw a decrease in bedding time of .4% and an increase in activity of 3 yards per hour. None of these results were significant to Strickland and his colleagues.
Strickland was quick to point out that 3 yards per hour amounts to just a few steps for a deer, “which isn’t much.” Certainly nothing like what hunters expected in a survey conducted by the Lab ahead of the study. In it, a whopping 83% of hunters said that the moon does influence buck activity, and on average, expected an increase in buck movement of 50-plus yards.
How Should We Look At the Moon Now?
For whitetail hunters thinking that the orientation of the moon will cause a buck to get up hours early to hit their plot, or make him keep him on his feet hours later in the morning before bedding down, or generally create lights-out action at a particular time...the latest science does not back it up. Two different factors associated with increased buck movement—cold fronts and the rut—are far more influential and can be backed with significant data.
That said, for moon believers that pour over nuances of buck behavior each fall looking for any little advantage, there may be a silver lining. The MSU study offered some data suggesting that when the moon is in a minor window (near the horizon) bucks bedded around 7 minutes later than usual—maybe enough to make a difference when set up tight to a bedding area. Also, the focus of the study was not on outliers. Keeping meticulous records of specific bucks with an eye out for out-of-the-ordinary behaviors may still pay off with a tell you can capitalize on. But for hunters that like to leverage hard data for high-odds hunts, putting all your chips on how the moon is hanging in the sky probably isn’t your best bet.
