As fawns are beginning to hit the ground, I am reminded of a deer breeding study from the early 90’s in which I was a participant. While it was a limited study, the data gathered helped to debunk some myths.
The rut is the common term that hunters use to describe the breeding activity of bucks. A doe will breed once a year in the fall. If for some reason she does not conceive on the first try, she will come in heat again about 28 days later. If she misses again, she will repeat this cycle until bucks lose their antlers in late winter.
There is a lot of misinformation about the timing of the rut among hunters. I have heard it mentioned that when the first good norther comes down, this will trigger the breeding cycle. I have heard the first full moon in a given month will get things started. Well, I have news for you – no matter the moon phase, nor the temperature, that doe will get bred.
I would like to share with you some limited data I have on the runt and it’s timing in Southeast TX. In 1993, I participated in a study that was intended to find out exactly when deer are breeding throughout the State of Texas. I want to share this local data with you. It was collected by Wildlife Biologists with the Texas Parks and Wildlife Department with help from select landowners across the state.
Following are the numbers from Colorado County: 16 doe were harvested on the Bonahm, Crier Creek, Tait and Holman Ranches. Of the 16, twin fetuses were found in 13. One had no fetus. This particular deer was one- and- a- half years old. Two had only a single fetus and one of these was a 15.5 year old doe that had a known age since it was freeze branded as a fawn on the Tait Ranch. So, on the 16 doe in the study, there were 28 potential fawns.
The fetuses from the pregnant doe were measured. From this data, the time of conception could be calculated. Six of the deer were bred in October with the earliest being October 15th. Nine were bred in November and the latest date of conception was November 28th, but this was from a doe on the Crier Creek Ranch (game fenced) that had been transported to the property from South Texas, so it is not a fair indicator of the rut for this area. Excluding the South Texas deer, the remaining doe were all bred by November 6th.The average age of the doe in the study was 3.9 years.
this information we can tell that the peak of the breeding season for whitetail deer in Colorado County is the last week of October and the first week of November. Below is more data from nearby counties:
Fayette County: 10 doe harvested and all but one had twins. The earliest date of conception was October 17th and the latest was November 13th.
Lavaca County: Only one doe was entered into the data and it had twins and the conception date was October 2nd.
Waller County: Three doe harvested and all had twins and all were bred on November 14th or 15th.
One should note that except for the Crier Creek transplanted South Texas deer, only two out of 27 local deer were not bred by December. This breaks down as 93% of the doe were pregnant. That information throws sand on a lot of people saying there are not enough bucks out there to breed.
Another useful bit of information this study shows us is that the majority of fawns will be hitting the ground the last two weeks of May. If you are a rancher and are concerned about these babies you might work with this bit of knowledge when planning your hay cuttings so as not to accidentally kill these fresh fawns.
I have seen bucks start to get very active the end of September. These guys can sense the time is about right and are getting ready for the breeding cycle. Science has taught us that decreasing daylight is the true trigger for stimulating the rut. The overall physical condition of the doe segment has a small influence on timing as well. Usually, if the deer are fat, the rut will be a few days earlier. It just so happens this time of the year is when the first crisp cool fronts roll south. So by accident, the majority of hunters feel the weather is the trigger. It might be that deer are somewhat like people in that the cooler weather will make the deer “feel good” so they may stay out and be a little more visible at this time.
One final fact about breeding dates. When you see bucks chasing doe in late December, what you are witnessing are fawns that were born back in May becoming sexually mature and coming into heat. Historically, the last week of the rifle season has been when our family and guests have taken the largest bucks on our River Ranch near Columbus. Moral of the story is to not give up hunting until the final minute of the season if you are after a trophy.