By Jason Snavely
Popular hunting magazines, including this one, are full of articles with headlines such as Hunting the Trickle Rut, How to Hunt the Late Rut, Rut Predictions and the ever-controversial Plan Your Rut Hunt by the Moon.
Yet, as hunters, we misunderstand the rut as much as we love it. Scientists who have spent decades researching and dissecting the whitetail rut readily admit there’s much more to unravel. So, is the rut really predictable? Does the moon really affect buck movements during the rut? Well, let’s review the science so you can decide whether your rut-hunting strategy needs an overhaul.
Before you can hold up your end of a campfire rut debate, it’s important to understand the “why” surrounding the timing of the big show — from nature’s point of view, not your hunting buddies’ point of view. We hear it all the time, “It’s an early rut this year,” or, my personal favorite, “We didn’t have a rut this year!” I’d like you to be educated on the herd and habitat conditions that affect the timing, intensity and duration of the rut. But first, let’s stir up the hornets' nest and get this moon business out of the way.
Should you plan your rut hunts around lunar phases and/or positions? I hear this question often. While there seems to be solid evidence that lunar (moon) phases and cycles influence movement and behavioral patterns of some species (horseshoe crabs, various fish species, oysters), there is a lack of “good science” that identifies and supports a positive association between lunar factors and deer movements. Studies on this topic date back to John Alden Knight’s 1942 book, Moon Up-Moon Down; however, there are no clear correlations to any of it!
I’ll never forget when deer managers and biologists — myself included — got excited momentarily when a 2016, peer-reviewed paper on deer movements and the moon was published in the Journal of Southeastern Association of Fish and Wildlife Agencies. To date, this paper is one of the few that actually addresses this topic directly. However, the scientific community sort of discarded it as quickly as they welcomed it. The authors radio collared 38 South Carolina bucks ranging from 1 to 4-plus years of age, and their locations were recorded every 30 minutes. As I read through the abstract summary that precedes all of the “sciency” jargon, it appeared as though the researchers discovered that the popular solunar charts do, in fact, predict periods of increased activity in whitetails.
However, the very next line of the abstract confused me, as the authors seemed to backtrack by reporting, “Our data suggest events identified by solunar charts have some association with deer activity; however, the relationships between lunar events and lunar phase expressed in solunar charts may be misleading.” Therefore, we really haven’t accomplished anything other than the need for more research.
Let’s be clear; there are absolutely zero peer-reviewed, replicated studies that prove the moon (phase or position) impacts deer activity to the extent you can capitalize on increased harvest opportunities. In other words, I wouldn’t advise you to gamble your vacation time around it — unless it just happens to fall around the peak of your local rutting activity, as it so often does. By default, if you spend more time in the “rutting woods” based on the predictions from a lunar chart, you’re likely to experience more observations, and thus, more harvest opportunities.
Changing gears slightly, studies show that brightly illuminated nights from a full moon result in reduced nocturnal activity of prey species such as kangaroo rats and snowshoe hares, suggesting these species “feel” more vulnerable to predators under brighter conditions. As a result, research on this front also finds that the predators of these prey species display decreased activity on bright, full-moon nights due to reduced prey availability. Hunters generally report and accept that deer are more active on brightly illuminated full-moon nights, thus reducing daytime deer sightings, although I am not aware of any scientific proof. Obviously, as predators of whitetails, we can’t legally hunt them at night. So, this science does not apply to the predator-prey relationship hunters have with deer.
Proven Rut Factors
So, if the moon has little to no effect on deer activity during the rut, what does? In nature, species have developed physical and behavioral adaptations that enhance their survival and reproduction. Otherwise, their species is deleted! Unless you change latitudes, the timing and duration of your rut is likely very similar to what it was last year, plus or minus a couple days. Sure, short-term weather extremes can impact animal activity; however, those are insignificant and unpredictable.
Any significant shifts in rut timing are more likely to occur over a transitional period of two or more years, due to a change in overall deer density, adult age structure, adult sex ratio and/or nutrition. We’ve proven over and over that you can shoot your way to a more predictable, shorter and more intense rut. In other words, a well-managed deer herd with a balanced sex ratio and bucks that represent the various age classes tend to breed at a time that fawns drop precisely when nature provides a succulent spring bounty of food and cover.
If your rut is unpredictable, sporadic or appears to be nonexistent, your management plan (or the overall herd dynamics in your area) needs an overhaul. My experience is that hunters who hunt well-managed deer herds don’t feel the need to rely on “moon charts” but instead hunt an intense rut.
Rutting behaviors are physiologically driven. The overall timing of the breeding season is tied the timing of fawn drop, roughly 200 days after conception. In most of the whitetail’s range, fawn drop coincides with spring greenup and the appearance of lush, nutritive vegetative growth and cover.
The general timing of the rut is linked to photoperiod, the ratio of daylight to darkness in a 24-hour time period. Whitetails, being short-day breeders, synchronize breeding as the ratio of daylight to darkness declines (shorter days). Explaining this ratio got easier when weather apps started incorporating a pie chart to show the ratio of daylight and dark hours in a 24-hour period. When the daylight “piece of the pie” becomes smaller than the darkness slice, various hormonal processes are triggered in the reproductive physiology of the animal.
As with any interesting and popular topic that demands attention, there are numerous misconceptions and misunderstandings surrounding the rut. While popular opinions and theories are sexy, I’ll remind you they are just sexy anecdotal opinions and theories. Hopefully, this summary of biological facts regarding the rut will prepare you for those colorful camp conversations around the fire pit and allow you to separate fact from fiction.