New Research Confirms The Moon Doesn’t Affect Deer Movement

The theory that moon phase and position somehow affect buck movement has permeated our modern hunting culture for decades. In fact, hunters of all calibers (old school, newbies, and consistent big-buck killers) are all susceptible to this line of reasoning. After all, it’s hard to argue with a guy who has more bone on his wall than most folks have in their bodies. But does the moon actually get big bucks on their feet?

A recent study from the MSU Deer Lab at Mississippi State University might have solved the ongoing mystery surrounding these lunar theories. The paper version of this study won’t be available for another month or so (we’ll link it here when it is published), but you can watch the team at MSU Deer Lab break down their extensive study on YouTube, which I would encourage you to do. Otherwise, here’s a rundown of what they discovered.

The team at MSU Deer Lab (Natasha Neary PhD, Luke Resop, Dr. Steve Demarais, and Dr. Bronson Strickland) sought to find a definitive answer regarding the question of how the moon phase and/or position affects deer movement. They not only looked at the moon phase but moon position (overhead, underfoot), which plenty of hunters insist matters even more than the phase.

“Essentially, we’ve got two phenomena we’re working with,” Dr. Strickland said, “the luminosity from the phase and the position and its assumed effect on gravitational pull on deer, which either may stimulate or suppress movement.”

In other words, Dr. Strickland summarizes what hunters imply, even if they don’t realize it. When hunters claim that the moon has an effect on buck movement, they are suggesting that the brightness of the moon and its gravitational pull either hinder or increase deer movement.

For instance, one common theory surrounding buck movement and the full moon suggests that because a full moon provides more light, deer see better and thus become more active at night, leading to decreased activity or more bedding during the day. The opposite goes for a new moon, i.e. less light leads to less nighttime movement and more daytime activity.

Dr. Strickland noted that one of the challenges with this study is that some hypotheses about the moon and deer movement might correlate to a certain moon phase. In other words, someone might see—or not see—a ton of deer movement on a full moon. This anecdotal experience might lead to confirmation bias, i.e., I shoot a buck on a full moon, which means that the two must be related. In reality, these instances are a matter of correlation, not causation. Dr. Strickland equated it to rolling dice. You’ll eventually roll double sixes, but just because you’re wearing your red shirt while you do it doesn’t mean the two are related.

To narrow down the specific question they wanted to address, the team surveyed hunters (about 1,400 respondents) about theories on the relationship between moon phase/position and deer movement.

They started the survey with a simple “Yes” or “No” question: Do you believe the moon has some sort of effect on deer activity? Of those roughly 1,400 respondents, 83% said “Yes.” If a respondent answered “No” the survey simply ended. So the percentages that follow apply to the 83% that answered “Yes.” Of those that believed the moon has some effect, 25% believe only moon phase affects buck movement but not moon position, while 13 % believe only moon position affects buck movement, and the remaining 45% believe that some combination of moon phase and position affect buck movement.

Of the same 83% that said the moon has some effect on deer movement, 85% say that the moon phase/position would increase a buck’s yards traveled per hour. Similarly, 76% also believe moon phase position affects a buck’s bedding time, and 81% believe that moon phase/position affects what time a buck leaves their last afternoon bed, which the team analyzed.

The team also asked hunters how many yards per hour they believed the moon phase to affect deer movement. Hunters believed a significant change would show an increase of at least 50 yards per hour in buck movement rates or a decrease on “bad” moon days. Regarding time spent bedded, hunters said that a time of at least 30 minutes less spent bedded was also significant. Last, hunters believed if a buck left his last afternoon bed prior to sunset that would also demonstrate a meaningful change.

The theories, based on hunters’ responses, provided a framework of questions for the team to address in their study, which they did by tracking 48 collared bucks, many of which were mature, from September 1 to February 28 in Mississippi.

Natasha Neary tracked yards traveled per hour on all the bucks throughout an entire deer season during legal shooting hours to see if moon position or phase impacted buck travel. It’s important to emphasize the legal shooting hours parameter, since it’s the timeframe that’s actually beneficial to hunters.

First, we need to take a step back and look at deer movement in general. For context, Neary noted that over an entire season, bucks averaged about 265 yards of travel per hour and were bedded 34% of legal shooting hours. Outside of the rut, bucks traveled an average of 219 yards per hour and bedded 38% of daylight hours. However, during the peak rut, bucks traveled on average 400 yards per hour and bedded 23% of legal shooting hours. That means that bucks (on average) travel nearly twice as far per hour during shooting hours in the peak rut.

Dr. Strickland emphasized these data points because they are significant enough that we can see a tangible event like the rut directly affect buck movement, unlike theories surrounding the moon phase/position. The buck movement from the rut drastically contrasts the data from buck movement regarding moon phase. The yards traveled per hour almost doubled during the rut, while the time bedded decreased by 11%. These are significant changes prompted by the rut. Travel and bedding times related to the moon don’t even come close.

For deer movement related to the moon phase and position, the team calculated buck activity by looking at yards traveled per hour, bedding and leaving times, and the time bedded percentage. To record any differences in buck movement, they tracked variances in movement based on a two-week window of buck movement. The team then used the Solunar calendar’s rating system of 1-4 (worst to best) based on the percentages of new/full moon. So, a day rate of 4 would be the best day to hunt (if you believe in the solunar theory).

Results: The moon has no effect on buck movement.

Remember, of the hunters who believe the moon affects deer movement, most said that the moon phase/position should produce, at minimum, a significant change of bucks moving 50 yards per hour during shooting hours, and at least a half hour earlier from their last evening bed (before sunset).

It’s also worth noting that the GPS collars give a reading every 15 minutes, and that there could be a 10- to 15-yard difference in a buck’s actual position. If you want to look at a breakdown of buck travel in moon phase only, buck travel in moon position only, and buck travel in a combination of phase and position, you can listen to or watch the podcast. For the sake of brevity, here’s what they found:

On a day rate of 4 (the best) during a major window with a full moon, the team saw an increase of 4 yards per hour movement and essentially no change in bedding time. For minor times, the numbers are even smaller, with little to no change in bedding time. In fact, the strongest examples the team found were a few outliers, which included an 18-minute difference in a bedding time and a 10-yard increase per hour in movement. These were random observations at best. Again, there’s a possible 10- to 15-yard discrepancy in the GPS location, so these insignificant changes probably represent a number closer to zero.

There was also an inconsistent correlation between travel and bedding distance/times. One thing Neary pointed out is that if moon phase and position do have an effect on buck movement, then you should be able to observe a consistent pattern that includes an increase in buck movement and a simultaneous decrease in bedding and vice versa. However, that’s not what the data showed.

The changes in movement/beddings are so insignificant that most of the changes actually reflect zero. Luke Resop, a PhD student and team member who worked on this study, stated that this is essentially the data you expect to see when there’s no effect in a study. Basically, there’s no conclusive data to support a relationship between moon phase/position and buck movement. Dr. Strickland noted that the differences were “trivial” at best.

For starters, you can throw away that lunar calendar. Or keep it if you’re into relics and whatnot. Some bow hunters might be tempted to read some of these data points as significant, especially those who hunt close to bedding. But we’re talking about an extra four yards per hour in movement, and that’s if those data points aren’t just from discrepancies in the GPS readings. Unless you’re right on top of the deer, it’s not significant enough to matter.

Again, it’s important to remember that just because you do or don’t see deer on a certain moon phase or position doesn’t mean that it confirms those Solunar theories.

Regarding anecdata, Resop made a great point that, “we often ignore observations that contradict the patterns we believe exist.” In other words, you might ignore the fact that you killed a shooter buck on a full moon (a bad moon day), but you quickly double down on your theory when you don’t see deer. It’s a classic case of confirmation bias that many hunters, myself included, can fall into.

Even if you’ve hunted by moon phase and position in the past, this study should come as a relief. No, you don’t have to plan your hunting days around the moon, and statistically, the rut still gives hunters the best chance to shoot a cruising buck. If you still want to believe that the moon holds some magical power over deer movement, I guess there’s nothing wrong with that. For the rest of us, we’ll be in the woods.