There are many theories about the timing of the whitetail rut. In some years, it seems like the rut breaks loose all at once, and in other years, hunters will say it’s a “trickle rut” because they do not see intense rutting activity. Books have been written about the impact of moon phases on deer breeding activity, and some hunters are religious about planning their hunts around the correct moon phase for what they believe will be the best activity periods for rutting bucks.

Several studies on the movements of radio-collared and GPS-tracked deer have cast considerable doubt on any theory that links the moon to rutting activity. In fact, when you finish reading this, you will see that there is very little room for impact of moon phase on rutting activity.

The key to when deer need to breed has everything to do with when fawns will be born. In the northern half of the United States, the vast majority of whitetail fawns will be born during the month of May. This is very important to the survival of the species.

Fawns are the key to survival of the whitetail species.
Fawns are the key to survival of the whitetail species.

In the southern reaches of the whitetail’s range, you can see evidence of rutting activity in late October and November much like you do in the north, but you will also see the majority of the breeding take place during December and even into January in many areas. This has everything to do with the milder winters of the whitetail’s southern range. A fawn born in July in Texas or Florida, for example, has a pretty good chance of making it to adulthood. No so in Minnesota.

In Minnesota or Maine or any of the Canadian provinces, a “July fawn” would only be three months old when the first cold, snowy weather sets in for the winter. Their chances of making it through that first blizzard in November are pretty slim. However, a fawn born in May will have the body size needed and will have the time to grow the necessary coat of guard hair and put on the fat needed to tough it out through that first winter.

If you graphed out the rut, you would see that the breeding activity in the southern range of the whitetail takes place over a long curve and the peak is not as noticeable. Does may be bred any time from November through January. In the Canadian provinces, the peak of the rut is very pronounced and the vast majority of the breeding takes place over a two- to three-week period. In fact, there is about one week each year when the bucks are going bonkers and the does are getting bred in a chaotic melee of rutting activity.

The timing of the northern rut necessarily must take place over a short period of time in the fall, so the fawns will be born in a short period of time in the spring. Snowstorms in the north are common in April, and cold nights take their toll on tiny little fawns. Any fawns born while the nighttime temperatures are falling well below freezing have high mortality rates. Getting a foot of snow dumped on a newborn fawn is often a death sentence.

How do the deer know this? The rut is entirely controlled by photoperiodism. The length of daylight hours triggers the pituitary gland to release hormones and prepare a deer’s body for breeding.

Seeing bucks out and about during daylight is a sure sign that the rut is in full swing. Furious rutting activity causes bucks to throw caution to the wind.
Seeing bucks out and about during daylight is a sure sign that the rut is in full swing. Furious rutting activity causes bucks to throw caution to the wind.

The changing length of daylight hours are more dramatic the farther from the equator you get. In the northernmost habitats where whitetails live, there will be 20 hours of daylight at the day’s longest point in June, and there may be 18 hours of dark in the deepest parts of winter. That’s a dramatic change to take place over just a few months. On average, it is changing eight to 10 minutes per day.

In the southern parts of the whitetail’s range, the changes are not so dramatic. Days aren’t so short in the winter and nights aren’t so short in the summer. A change of a minute or two a day is enough to get from one end of the spectrum to the other.

These radical changes in daylight hours dramatically affect the pituitary glands in northern deer, so the rut comes on fast and furious and then it’s over just as fast.

So when someone talks about moon phase, weather, or any other influences over rutting behavior, we know that these factors are very minor and have little affect, if any. Those positions become very difficult to defend in the light of the importance of the timing of fawning. The rut in the South can be quite drawn out, but in the North, it must be compressed into a very short window of opportunity—the health and survival of the spring-born fawns dictate it.

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Images courtesy Bernie Barringer

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4 thoughts on “May and the Timing of the Whitetail Rut

  1. In both of my books “Hunting Big Woods Bucks” and “Big Woods Bucks Vol. II I write about the rut in Northern Maine being from the 15th to the 30th of November. I have been tracking bucks up north for 35 years and you can set your calendar by these dates. There have been several writer in the Northeast trying to convince hunters that the moon controls the rut so I’m glad to see the proof of what most of us know.

  2. While what Mr. Barringer states may well play to the masses, he offers no scientific data to back any of his claims. I’ve written four books on whitetails and devoted 8 chapters in my book, The Deer Tracker’s Journey to how the moon indeed has a dramatic effect on the rut, and how it changes the breeding timing from year to year. I’ve spent over 40 years tracking bucks in Northern Maine, and many other Northern locations and I find no proof substantiating what has been written by some who think they know without doing any research. Just because you happen to hunt doesn’t make someone a reliable resource.

    1. I don’t know how much the moon effects has on the start or duration of the rut. It does, however, effect what time of
      day they are most active. Deer are more active at night during the full moon period and thus are less active during
      the day. A new moon during the rut is the best time to be in the woods although anytime is a good time to be in the

    2. There have been many studies that show the moon has no affect on the timing of the rut. It’s one of the greatest enduring myths of whitetail hunting.

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