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Rut

Lessons Learned From The 2016 Deer Rut

by Dr. James C. Kroll   |  November 15th, 2017 0

Last fall’s rut was one of the most frustrating of any in the 56 years I’ve hunted. Before the season I knew great challenges were coming, but they still exceeded my expectations.

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Odd lunar cycles, drought and other factors cut into last year’s visible rutting activity, in the author’s opinion. (Photo by Ron Sinfelt)

The season started out great. Accompanying North American Whitetail Editor in Chief Gordon Whittington to Wyoming’s Solitude Ranch & Outfitters, I’d used my TenPoint crossbow to take a monster buck in September. But then things generally headed south.

Mid-November found me and a cameraman returning to Dawson Springs, Kentucky, to rifle hunt with my friend Larry Porter of Ken-Tenn Hunting. Larry does a superior job of not only managing his properties but also maintaining the quality of bucks that live on them. I’d taken some good deer with him and was eager to get another one in 2016.

As the hunt unfolded, I shared with Facebook friends and followers what I was seeing, the strategies I was using and why I was using them. On North American Whitetail TV presented by Quick Attach, my normal goal is to harvest a mature buck, and I’d never strayed from that. But last fall I decided to set the bar even higher: a true trophy buck, all or nothing!

I couldn’t have picked a worse year to make that declaration. None of the big deer known to be in that spot in Kentucky moved in daylight that week. But finally, after two days of scouting and eight of hunting, things began to move in my favor.

On the last evening of my hunt, an old patriarch finally walked into a Buck Forage oat plot with a few minutes of light left. At long last, I had a chance. Unfortunately, although very old, the buck lacked a big rack. He wasn’t the deer I was after. And so, as light was fading, I chose not to shoot. I was the one who’d set the goal, and I’d have to be the one to live by it. (Interestingly, not a single person sharing the experience with me on Facebook told me I’d made the wrong call.)

In December I did take another monster on a friend’s low-fenced South Texas ranch, and I followed that with a close call on a legitimate Boone & Crockett buck at Bar J Ranch. On the latter hunt I was using a Smith & Wesson Performance Center .44 Magnum handgun, and the deer appeared at 15 yards. However, we’d just run out of camera light. I had no choice but to pass.

Don’t get me wrong — I’m thrilled with the deer I shot last season. But overall, it wasn’t a good year for antler growth, and even during the rut daytime buck movement seemed lower than usual. Why?

SETTING THE STAGE FOR TROUBLE
I’ve spent most of my adult life living with and studying whitetails. Using high technology, good observation skills and a lot of boot leather, I’ve learned a great deal about what makes them tick. This especially is true of bucks. Although there’s always more to learn, we’ve managed to dig out many of the factors that make whitetails do what they do.

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The author checks a Texas live oak for ripening acorns. Combined with drought in many areas, spotty mast production last fall hurt some deer herds. (Photo by Gordon Whittington)

The species’ behavior is mediated by two primary senses: smell and sight. A whitetail’s nose is far more acute than its eyesight. However, the eyes play a critical role in regulating behavior. Light is what signals a special part of the brain that regulates hormonal activity. Light also influences when and where deer travel. They tend to stick to the shadows and darker portions of their habitat. And being mostly nocturnal, the whitetail is heavily influenced by moonlight.

The moon plays a critical role in the timing of behavior and physiology, but not in the way many people think. Deer aren’t fish. Solunar tables and such might work well for predicting when fish will bite, but in my research, I’ve never seen that deer respond to tides or gravitational pull. These forces are meaningless to them. Every scientific study we’ve conducted at the Institute for White-tailed Deer Management & Research has failed to support any predictability between moon position and deer activity.

However, the phase of the moon can have a profound effect on when the animals move and breed. Our research clearly showed that each subspecies of whitetails would “prefer” to breed three to five days after a specific full moon. Which full moon is determined genetically; Midwestern deer tend to breed on the November full moon, while deer in South Texas and northern Mexico cue on the December full moon.

It’s fortunate we learned this many years ago, because many whitetail populations today are a hodgepodge of genetics resulting from restocking efforts. East Texas received some of the Avery Island subspecies of the Gulf Coast (October breeders) and others from the South Texas Brush Country (December breeders). The result is a permanent “trickle” rut of does coming into heat over a long period, as opposed to a single sharp peak in breeding each fall.

To further confuse matters, whitetail populations reached saturation in most areas by 2000. Numbers in many areas now are lower, and they probably will remain below the previous peak, due to habitat degradation. Nutritionally stressed deer can’t conform to what their genes “tell” them to be or do.

The moon of course is constantly changing. But there’s total predictability to its cycle. For instance, a full moon always rises around sunset and sets around sunrise; a new moon is the opposite. (By the way, my favorite moon phase to hunt is the last quarter. During those few days of the monthly cycle, the moon rises around midnight and sets around noon. During this phase, deer to move some prior to nightfall.)

Like many other animals, whitetails calculate day length in a reverse fashion, by measuring the length of the night. The culprit is melatonin, a chemical produced by the pineal gland. It influences reproduction and other activities. Light inhibits melatonin production, so as the days shorten, the pineal gland produces more melatonin, which then is measured by the brain to determine day length.

Studies have shown that moonlight can also impact melatonin production. Concentrations are lowest during a full moon and highest during a new moon. Melatonin also has a profound effect on reproductive hormones.

For a whitetail hunter, this creates the question: “What’s the impact of varying moon cycles?” Midwestern deer are wired to breed around the middle of November, allowing fawns to be reared at a time when forage is most abundant and nutritious. Day length is tied to the calendar, of course, but the timing of the full moon in any month varies from year to year. In the past three Novembers, the full moon has fallen on Nov. 6 (2014), Nov. 25 (2015) and Nov. 14 (2016). Faced with such variability, deer can rely on their internal clock to try to breed at the proper date — but the greater the variance, the less accurate the internal clock.

In 2016, we saw two lunar phenomena that threw things off even more: a “blue” moon and multiple “super” moons. On May 21 of 2016 there was a “seasonal” blue moon: the third of four that spring. (The more common modern definition of a blue moon is the second full moon in the same calendar month.)

A super moon occurs when the moon is closer to the earth than its average distance, greatly increasing nighttime illumination. Last year’s three super moons were on Oct. 16, Nov. 14 and Dec. 14.

The bottom line of this lengthy discussion of the moon is that if you were a deer in 2016, your brain had a rough time deciding what you to do and when to do it!

Earlier, I intimated that body condition might have an equal impact on deer behavior, especially the breeding cycle. It’s safe to say that in order to be ready for the rut, a whitetail must undergo a number of physiological changes.

First, all deer must change from a summer to a winter coat. Next, does must restore body reserves after a season of nursing, while adult bucks finish mineralization of antlers and prepare for combat by increasing muscle mass. And finally, the brain must be primed to start the reproductive cycle.

All these steps must happen in perfect order and, in most cases, completed before the next. A deer entering fall in poor physical condition will have difficulty preparing for the breeding season. Body condition at the end of summer is determined by several factors, including the condition the deer was in coming out of the previous winter and the availability of critical nutrients throughout the growing season.

In any given month for the entire 2016 growing season, some part of the U.S. was suffering from drought conditions. Also, extremely dry periods were often interrupted by sudden heavy rainfall, producing a rather “schizophrenic” climatic pattern. This of course played havoc with deer forages and the mast crop in many locations.

Our institute’s early studies on deer movement also showed a significant impact of temperature, especially in fall and winter. Most Septembers I can count on hearing from numerous hunters and deer managers worried that buck numbers are down. This certainly can be true, but the same folks often contact me again later to report a sudden increase in buck sightings as temperatures decrease.

If the person seems puzzled by this, my response is, “If you had to gain as much as 30 percent more body weight and then wear a heavy fur coat 24/7, would you feel like moving around when the temperature is 80 to 90 degrees?” Warm temperatures can reduce deer movement during much of the year. In summer, a heat wave also can affect food consumption by bucks; in fall, of course, they restrict most movement to night.

My firm conviction is that the months that have the greatest influence on a given deer season are July to October. This is the time span that determines the condition of deer during hunting season, which in turn directly influences the rut and overall movement.

IN CONCLUSION
Essentially, what happened in 2016 was a perfect storm in which multiple factors (some varying by geographic region) combined to make the hunting tougher than we’d all have liked:

* Many whitetail populations continued to be in lower overall physical condition, due to overpopulation.

* In many areas, they’d also come out of winter in poor condition.

* Lunar timing — a “blue” moon and three “super moons” — greatly impacted the rut.

* Climatic conditions affected the availability and quality of deer foods during the growing season.

* Abnormally high temperatures during hunting season affected daytime deer movement.

Again, what made the 2016 season frustrating was that I was aware of these factors beforehand but didn’t make the right moves to overcome them. So what did I learn that could help me here in 2017, and beyond? That will be the focus of Part 2 in the November issue.

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