Has the Whitetail Rut Become Abnormal?

Posted on January 21, 2014

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“Like it or not, the “normal” rut conditions of the past few decades don’t match up with what many hunters have experienced in the last several years.”

                                                                 Dr. James C. Kroll

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If you are of the belief that the rut transpires during the middle of November with peak breeding on the 15th, than yes, it would seem abnormal. For decades now we have been conditioned to think so, thanks to the biological community, which in many instances still holds tight to this long-standing belief. However, as hunters have ‘evolved’ and gained a much greater understanding of whitetails behaviorally, and become more  discerning regarding what is or is not happening during their hunts, it has become apparent that the deer aren’t doing what they are ‘supposed’ to be doing, when they are ‘supposed’ to be doing it.

As a result of this I’ve heard any number of rationales, from well thought-out theories to the absolute absurd. Before we move one step further, please understand the whitetail rut transpires annually at the precise timing of a wise Creator who intuitively designed the entire sequence of events.  Kroll insightfully writes, “In my view, the reason some scientists don’t believe as I do about full moons and their effect on whitetail breeding is they’ve been studying abnormal, habitat-saturated deer herds most of their career. Those have become the new normal.”

Rut Timing

 

For those of you unacquainted with the research Charles Alsheimer, biologist Wayne Laroche and I have conducted over the past two-decades, here is the result of our findings: The 14-day breeding window, the time frame when 70-80% of the adult does will enter estrus, begins five to seven days after the second full moon (rutting moon) following the autumnal equinox (Sept. 23). This scenario holds true the closer to November 1 the rutting moon falls, intensifying the rut and facilitating a more predictable breeding timetable. The light of the full moon is the visual cue that stimulates the bucks and as it waxes over the next 5 days, the darkening nights trigger the does to begin ovulating. DSC_4772

In years when the second full moon after September 23rd falls on or later than November 14th, the less intense the rut will be. This is commonly referred to as a trickle rut. Breeding will begin closer to this full moon when this scenario presents itself.

The foundation for this belief is best explained by Laroche:

If the moon provides the timing mechanism for the estrous cycle, what sensory pathway in deer receives the lunar cue? External stimuli fall into three primary categories: physical, chemical, and biological. The great distance between earth and the moon rules out any regular 28-day exchange of sounds, scents or chemical and biological materials whitetails can detect.

The moon affects the earth’s gravitational fluctuations and nighttime illumination. Both factors create external stimuli that deer might detect. However, little evidence suggests deer or other creatures directly detect gravitational forces.

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Moonlight can be detected, especially by whitetails, which have eyes adapted for low-light vision. Light passing into the eye strikes the nerve-rich area in the back of the eye, causing electrical impulses to pass along the nervous system to various organs. Some impulses pass            to the pineal gland in the center of the brain, and provide input to the endocrine system. The pineal gland and related hormones are involved in or regulate the reproductive cycle. The pineal gland responds to light by increasing (with diminishing light) or decreasing (with increasing light) production of a hormone called melatonin. This, in turn, increases or decreases other hormones.

The fact moonlight changes the earth’s illumination on a cycle similar to the whitetail’s 28-day estrous cycle, the fact whitetails have a sensory system that can detect moonlight, and the fact the whitetail’s endocrine system responds to light stimuli by altering levels of reproductive hormones argue against coincidence.

Variables

 

As is the case with all science when not conducted within a controlled environment, nothing is completely exact. The whitetail rut is no different; there are external circumstances that can and do play a role in how the rut plays out in any given area. This is where it pays to understand herd dynamics, densities, habitat and even weather where you are hunting. Several influences can and will suppress deer activity during daylight hours. Weather and temperature are two of the biggest contributors that can make or break a frenzied rut. If an extended period of rain or snow is predominant, breeding activity might occur earlier as dense clouds shorten day length or be delayed due to the deer’s reluctance to move under such adverse conditions.

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When the temperature rises above 45 degrees, whitetail activity shuts down. The deer will continue to breed only now it will transpire entirely under the cloak of darkness when it’s much cooler.

Another factor attributed to curtailed deer activity during daylight is human pressure. If hunter densities become increased, whitetails are quick to respond by diverting their movements to nighttime.

If the buck-to-doe ratio becomes greater than 3 does for every antlered buck, competition amongst rivals is significantly diminished thus negating the bucks need to search for available does. When those does are spread miles apart in the big timber, that buck has to travel great distances in his search. On the other hand, if there is an abundance of competing bucks the action can and will begin early and in earnest making for an exciting time to be in that section of woods for the hunter.

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Kroll wisely pointed out what we know to be true even today:

Hunters spent most of the 20th century dramatically altering the population dynamics of whitetails through so-called traditional deer management (TDM) in which the heaviest harvest pressure is exerted on bucks. This mentality unfortunately lingers in many places. The result is high deer numbers with skewed sex and age ratios.

TDM has led to an increasing occurrence of trickle ruts. In some cases, does have to cycle 2-3 time before being bred. Add in the impact of changing climatic conditions, affecting both food availability and deer movement, and the stage is set for more difficulty finding a mature buck to shoot.

The 2013 Rut

This year’s rut played out as predicted, a few does bred around the first week in November through the 13th  with the bulk of the breeding taking place from November 14th through Thanksgiving week. This similar scenario last played out in 2005. We’ve found that when a full moon arrives after November 14th the rut truly is a trickle, meaning an ebb and flow of breeding activity. Hunters have been talking about a trickle rut for decades, with few understanding why there are years when the rut doesn’t seem to happen as they envision. We are saying that it’s because of when the full moon falls.

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After 17 years of studying this we’ve concluded there are three types of ruts:  A synchronized rut (when the full moon arrives the end of October to about November 7th) and is the most intense because a does’ estrogen level and a buck’s testosterone level peak November 1st, so everything synchs. Then there is a traditional rut when the full moon arrives from about November 7-14. We give it the name Traditional because this kind of rut pretty much matches what the biologists refer to as the rut (breeding) and what the “old timers” felt was the perfect time to be hunting rutting whitetails. A Traditional Rut is great but it never seems to match the intensity of a Synchronized Rut. Then lastly we have what we call a Trickle Rut when the full moon arrives November 15th or later. When this happens you’ll find breeding taking place from late October through the end of November……a lot of hot and cold periods, or ebbs and flows.

The reason many biologists and hunters have a difficult time getting their arms around the moon’s influence upon the annual whitetail rut is due largely to the fact that almost no one has spent the time studying the subject closely for consecutive years, nor do they have the funding to conduct such research.

Conclusion

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Although it is being touted by Kroll as ‘The New Normal’, is there really anything new? Despite some within the industry making attempts to rebrand or redefine an old product with new terms, it is really the same rut. What I believe has begun to transpire is that educated hunters have come to the conclusion that indeed, the rut transpires annually at different times each autumn and are now systematically beginning to put the pieces together. When that timing can be predicted with accuracy going forward, the how’s and why’s of the event aren’t nearly as important…now you’re hunting bucks when they’re most vulnerable…consistently.

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Posted in: Whitetail Deer