I’ve been hearing this in deer camps for half a century: “Full moon, boys. Deer won’t be moving this morning. They fed all night.”
You’ve probably heard or read statements like that. Heck, you’ve probably made them. It’s common knowledge. With the moon shining big and bright, deer can roam, rut, and feed all night. And then they hole up all day, frustrating hunters. Everybody know this.
Except it’s not true.
FULL MOON DEER STUDY SHEDS LIGHT ON THE SUBJECT
A recent study by PennState monitored movement of female adult whitetails fitted with GPS tracking collars during the month of October. They were wild, free-range deer on public forests. During full moon nights they moved less than on nights when the moon was dark (called a “new moon”). That’s the opposite of what we’ve all been told! Under the full moon deer moved less, not more. But—here’s the kicker—the difference in movement amounted to an average of just six meters per hour.
Six meters? I can cover that in six steps.
More significant was when deer moved. They averaged about 60 meters of movement per hour until about 6 a.m., when movement spiked quickly to peak at about 125 meters per hour at roughly 7 a.m. It then declined to 45 meters per hour at 10 a.m. Evening activity showed a similar spike starting at about 3 p.m., peaking at about 6:30 p.m. and dropping sharply toward minimal movement at about 8 p.m. New moon, partial moon, full moon. Didn’t matter.
EATING DRIVES FULL MOON DEER ACTIVITY
This makes perfect sense when you think about whitetail physiology. They are ruminants. It takes them from one to four hours to fill up, depending on forage abundance. In a green wheat or alfalfa field with great forage everywhere, they might stuff themselves without moving more than a few yards. In poor habitat they might have to walk several meters from one useable forage plant to the next. Either way, their maximum movement will be while transitioning from bedding cover to feeding grounds and back again. The daily commute. I’ve watched them hike a mile to accomplish this.
After filling their rumens (first “stomach” in popular parlance) they bed and ruminate, i.e. regurgitate and re-chew what they took in. This process takes about four to six hours with, perhaps, some stretching and nibbling every few hours. Soon after, feeling hungry again, the deer travel back to a major feeding site.
Tick tock, tick tock. Like clockwork this cycle moves through the days, months, years, millennia. Deer movement is largely determined by their digestive systems coupled with their preferred initial foraging times, dusk and dawn. If something forced them to eat at 10 a.m. instead of 7 a.m., their digestive process would signal them to feed again at about 1 p.m. But there is no way they can “feed all night” to stoke the fires against the need to move all day. Moonlight or no moonlight, deer movement is slave to deer digestion, and that’s been standardized for a lot longer than we’ve been hunting them. Deer have adapted to be most active at dusk and dawn (crepuscular), and their physiology maintains that.
DIRECT OBSERVATIONS BOLSTER THE STUDY
I’ve had opportunities to watch undisturbed whitetails feeding in lush forage. The same animals would routinely hike from distant bedding sites to the feeding site, feed within a small area, often no more than 30 yards by 30 yards, then bed right there at dark. We would check on them by spotlight at various times from dark until 10 p.m. to find them bedded and ruminating. Around midnight many would rise to stretch and nibble. Sometime between 6 a.m. and 9 a.m. most would rise to again feed heavily for a couple of hours before moving off to a distant bedding spot. This would repeat night after night. Same deer, same spots, same routine. Until a coyote or human hunter barged in to disrupt the program.
Of course, where deer bed and feed changes due to seasonal forage availability, but those dusk and dawn activity periods rarely do.
DOES THE RUT ALTER FULL MOON DEER ACTION?
We can argue that the PennState study didn’t track bucks and didn’t track during the rut. Those are valid points. Doesn’t it make sense that bucks will rut hard all night and then lay up to recuperate all day? I doubt it. Does can reach estrus at any hour, and once they do they are available for about 24 hours. Competition for their favors at this time is fierce. This is why you often see bucks wandering at all hours of the day in mid-November. Expecting a buck to skip a day of chasing does because the moon was bright the night before is like expecting 21-year-old single men to stay home on Saturday night because Friday was sunny. Bucks are much more active during the rut, but hormones and the need to breed are the cause of that. Not moonlight.
HOW SHOULD YOU DEAL WITH FULL MOON DEER?
The “take away” for hunters? Continue to expect dusk and dawn deer activity. Know that once the daily migration from bed to dining hall is completed, the animals will be feeding for as many as four hours. They will then look for a place to hide and ruminate. This makes the 8 to 10 a.m. and 6 to 8 p.m. slots—surprise!—high-activity periods. When the rut kicks in, know that buck movement will increase at all hours and bucks will often move far from their usual haunts. The sight and scent of estrus does will lure them anywhere, anytime.
As for the full moon, expect it to rise at sunset once each month, twice in a blue moon. (About every 2.7 years we get two full moons in one month, and the second is called a blue moon.) Enjoy its beauty. But don’t worry about what it’s doing to the deer, because the answer is “nothing.”