Predicting the rut is one of the hottest topics in whitetail hunting. You don’t need a crystal ball, tea leaves, or chicken bones to predict it. To accurately predict the breeding season we must first understand the why’s, where’s, what’s, and when’s of the rut. After that it’s a simple matter of math. As much fun as rolling the chicken bones might be, it probably won’t get you any closer to predicting the rut.
Even though the rut is the best time to harvest big bucks, the breeding season is truly all about the does. The rut serves one purpose: to perpetuate the species. To best understand the breeding season, we must look back through the eons of time and see the myriad natural factors that affect it.
The Evolution of the Rut
The Weather Factor
The last Ice Age occurred ten thousand years ago. Due to the severity of winter across most of North America, the deer had to adapt to a narrow fawning window of about two weeks each spring. Fawns had to be born late enough so their mothers could recover enough strength to nurse them. Yet, they needed to be born early enough to be able to gain sufficient body weight in order to survive the coming winter.
As deer evolved, Mother Nature played an important role in the timing of the deer breeding season. Survival of the species depended on a proper season of rutting.
Because of the severe energetic costs of lactation, the birth of fawns is typically correlated to the availability of highly nutritious forage.
For the first few days after birth, fawns nurse two or three times during daylight hours. Nursing becomes less frequent as the fawns begin to forage, and stops altogether after about four months.
The Predator Factor
In ancient times, predators were far more abundant than they are today. Predators limited deer populations. Fawns are exceptionally vulnerable to predators. Several years ago I came across a coyote den and found a dozen fawn hoofs in front of the opening.
Mother Nature’s response is to have as many fawns hitting the ground at the same time as possible. This further narrows the birthing window to about four days in late May or early June. An abundant food supply makes it virtually impossible for predators to wipe out the deer.
The size of the doe is another contributing factor in determining the rut’s timing. The average weight of a mature doe in the northwest and northeastern United States is about 135 pounds. In the Midwest, deer are a little bigger, averaging about 150 pounds. In the Deep South they’ll go maybe a hundred pounds. Size affects gestation periods. Midwest deer will have a gestation period of 200 to 210 days, while southern deer often give birth after only 190 days.
The average gestation period for a whitetail doe is two hundred days. All we have to do is to subtract two hundred days from the day the fawns are born and we’ll have a good idea of when the breeding occurred.
Most fawns are born in the last few days of May and the first few days of June. In my neck of the woods, the fawns are generally born between June 2 and June 4. That puts the breeding around November 15.
Most hunters are confused about when the actual breeding takes place, because the deer generally are not visible. Most of the rutting activity occurs at night. When breeding is going on, bucks and does are often paired and remain in some secluded sanctuary.
The best time to see big bucks is immediately prior to, and after, the majority of the breeding has taken place. A doe will only be in estrus for around twenty-four hours. After inseminating a doe, the buck will be on the move to find another receptive female. He usually doesn’t have to travel far. After the rut, when the bucks are looking for one last chance at "love," they are most visible and vulnerable.
“The rut is late again.” I hear this complaint at least every other year, but strangely the fawns are born at the exact same time each spring. Just as sure as the sun rises, the rut must go on.
Good Luck and Good Hunting,
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