Deer hunting can mean many long slow hours waiting for a deer to appear, or trekking miles over rugged terrain with nary a sighting. Then that magical time arrives when the woods seem to come alive. Ordinarily stealthy and secretive bucks seem to drop their guard and move about recklessly in search of a potential mate. It’s the breeding season, the whitetail rut.

When will the rut be this year? It’s an oft-discussed and debated topic among deer hunters. Theories abound on what triggers it and when it will occur and most hunters are anxious to hear the predictions as early as possible so they can schedule their valuable free time to focus on the period when deer, especially bucks will be most active and vulnerable.

It’s been a dry summer and plants might be stressed. Leaves might fall sooner. Hard and soft mast might be in short supply. Some will suggest this could lead to an early rut. It’s also been unseasonably warm, and could that delay the rut?

Amateurs and professionals alike have tried to solve the riddle of the rut. One theory claims rut timing is related to moon phase. We know that many physiological changes in deer are the result of photoperiodism, or changes in day length. As the days grow longer in the spring, antler growth rates increase. As they become shorter, waning hours of daylight trigger a slowing, then cessation, of antler growth. The velvet covering dies and peels off. These changes are slow and subtle.

The moon is also a source of light, albeit a more subtle source, being most intense during its full stage. Furthermore, moon phases vary from year to year. Could that not cause minor fluctuations in rut timing from one year to the next?

Many hunters believe it’s related to weather, more specifically temperature. “It’s been too warm, we need a good cold snap,” is a common sentiment when rutting activity is light or non-existent around the anticipated time.

Biologists have been studying every aspect of white-tailed deer for decades, including when the breeding season occurs. They do this in several ways but one of the most reliable is by taking fetal samples throughout the year. By measuring the fetuses they can back date and determine when that fawn was conceived. What they’ve discovered can be enlightening, especially for a hunter trying to schedule their vacation days to coincide with the rut.

All the research that’s been done in every state and province where whitetails occur has shown the same result. Peak rut or peak breeding dates vary geographically, particularly in southern states with longer day length and milder climates. However, for a given location, peak breeding occurs at the same time every year.

It may seem to vary as warm temperatures do suppress daytime movement. However, the deer will simply be more active at night. It’s also worth noting that breeding season doesn’t begin with the flick of a switch. It’s a slow, gradual process. Some does may enter estrus a month or more before the peak period, with increasing numbers coming into heat approaching that peak, and declining numbers after. When breeding dates for individual does are plotted on a graph it appears as a bell-shaped curve, high in the middle and tapering down on each side; but the middle is always around the same 7-10 day window, the same dates, every year.

In Maine, that window is around Nov. 17-23 for mature does, and a week later for yearling does. That doesn’t mean you won’t find a randy buck chasing a reluctant doe outside that window, but the odds are significantly lower. It also doesn’t mean you will witness that during the peak either. As noted, peak estrus for an individual deer may not fall under the apex of that bell curve and if you’re not in the right place at the right time you might miss the action. Still, with deer hunting as with gambling, your best bet is playing the odds.

Bob Humphrey is a freelance writer and Registered Maine Guide who lives in Pownal. He can be reached at: bhunt@maine.rr.com

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