The morning sun peeks over the horizon, illuminating the river bottom below. The crisp fall breeze rustles the remaining leaves that utterly refuse to let go for the winter. Two does and a fawn feed to the west through some standing soybeans the farmer left behind. A young buck mills about to the east in the short cedars. All seems right calm and peaceful in the world.
An estrus doe comes busting out of the cattails directly to the north, mouth open and tongue out. It blasts across the field, heading for the treestand on the edge of the thick cover up on the hill. Seconds later a big buck comes flying out of the cattails, hot on the trail. It’s the big 4-year-old buck you’ve been after all season.
They both run right by your treestand.
But you weren’t there because you didn’t do your research.
There are several theories out there on how to predict the rut. I’ve heard story after story on what triggers the rut. But there is only one spark that ignites the big rat race. But more on that in a moment. First up, the myths of the rut.
False Theory No. 1: Temperature Triggers the Rut
I’ve heard so many times throughout my life that if it’s hot outside, the rut won’t start. Not true. When it’s time to breed, deer will breed. I don’t care if it’s 70 degrees or 10 below. When it’s time to do the deed, bucks will answer the call. There’s plenty of data to show that temperature does not trigger the rut.
The truth: All of that said, I can understand where people think that temperature can trigger the rut. Because on those hot days, the likelihood of seeing a lot of chasing and movement is minimal. Deer don’t move about as much during extended periods of unseasonably hot temperatures (The first of those days is another story.) So, deer are still breeding and chasing. They’re just most likely doing it in thick cover where it’s shaded, near water sources where it’s cooler, and under cover of night.
False Theory No. 2: Moon Phase Marks the Beginning
The truth: What is much more likely to be true, and has some data to support it, is that moon phase has the potential to affect how much rutting behavior hunters witness during daylight hours.
False Theory No. 3: Herd Structure and Sex Ratio Start It
This theory isn’t as common as the first two. But it’s out there. And I’ve herd it used on numerous occasions. While it’s likely the least common of the three, it’s also the most ludicrous, too.
The truth: Herd structure and sex ratio do not kick off the rut. However, these factors do have the ability to influence how long the rut lasts. Areas where the buck-to-doe ratio is off kilter will experience a prolonged rut, where does may cycle into estrus a second time — possibly even a third — before they’re bred.
The Best Answer: Photoperiod
The fact remains that we are still learning about the rut. Biologists and researchers are working around the clock to learn more about the complex machine that is the white-tailed deer. But the best answer to the “how to tell when the rut will be” question is this: The longest-running, most-proven, and best-supported theory with the largest amount of statistical data behind it is the theory of photoperiod. Daylight length is what drives deer to breed. And the research shows deer in the northern half of the country within given populations do so about the same time each year.
In the northern states, deer have to breed within a specific (and relatively small) window in order to give fawns the best chance of survival. In the southern states, it isn’t as important because of warmer temperatures and longer growing seasons. That’s why deer herds in the South breed anywhere from July (Florida) to February (pockets of coastal state deer).
How do we know this to be true? Back-dating fetuses. Biologists pull fetus samples from harvested does every season and their findings have been quite revealing. In the North, they’ve found that populations of does will breed during the same small window every year. Peak breeding varies slightly from population to population, but varies only slightly and seems to be directly effected by photoperiod.
Where the discrepancies often come into play is observed rutting behavior, not actual breeding. Observed breeding behavior by hunters is during daylight hours. But not all rutting behavior occurs during daylight. Weather, temperature, moon phase and hunting pressure all have the potential to influence rutting behavior and encourage deer to exhibit said behavior at night instead.
The Best Bet for Your Vacation Days
The best way to tell when the rut will be where you hunt this year is to contact your local biologist and ask what the research shows. Hopefully he or she has conducted research by back-dating fetuses and can tell you when local populations of does within that county/region have conceived in the past.
Once you have that information in hand, you can almost bet the seven to 10 days leading up to that peak breeding date will put you in the best action, also known as the chasing phase. Choose a few good stand locations and get ready. That window of opportunity, just prior to peak breeding and when bucks are chasing does, is the best time to kill a good deer. And they're the best days of the rut. That’s what I’d put my chips on when putting in for vacation this fall.
The fact remains that we still don’t know everything about the rut. But we now know enough to say with confidence that through research, photoperiod is the best answer to the start of the rut.
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