The Rut in White-tailed Deer
- Breeding Success and Fawn Survival
- The Early and Late Ruts
- The Rut by Geographic Areas
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The Rut in Texas White-tailed Deer
The following was based on three years of data collected by Wildlife Technicians and Biologists throughout Texas. Our goal is to get the information out to the hunters and landowners who assisted and helped fund the project. You may have seen parts of the article in outdoor magazines.
This project was funded by Texas Parks and Wildlife Department through Federal Aid in Wildlife Restoration Project 95, W-127-R.
The phenomenon known as "the rut" is the period when deer breed. People often ask biologists when the rut is going to occur. It's a question biologists commonly hear in the fall. Many hunters want to make sure that they plan hunting vacations to include that magical time when bucks lose all caution and deer are moving.
Can hunting the rut help? You bet. Anything that encourages bucks to move enhances the chance of seeing one. Buck deer, like most male mammals, seem to lose a lot of their natural caution when the scent of a receptive female is in the air. One of the tips gained from this study is that rutting bucks can be found during most of the hunting season in many regions of the state. Consistently successful hunters spend a lot of time in the field throughout the hunting season, not just during the peak of the rut.
Hunters and ranchers often encourage Texas Parks and Wildlife to move the season later to give deer a chance to breed. The study showed that no matter when the rut occurred, the vast majority of does were bred. Individual ranch and deer herd management are much more important than timing of the hunting season. The data will assist TPWD in determining whether the number of bucks in an area has an effect on breeding season length and success. There are many interacting factors which affect breeding.
The breeding study involved the examination of 2,436 does, the largest number of deer ever utilized in a Texas breeding study. The date of conception can be determined by looking at fetus length. An average of 200 days from conception was used to determine fawning dates. Biologists got as much information as they could from the does collected. They looked at the timing of the rut and at breeding success on 16 study areas throughout Texas for three years.
All years were combined to produce the graphs that show the rut timing. In most areas the rut varied very little from year to year. You can use the map and graphs to determine the timing of the rut in your area of interest. Will the information help with the planning of your hunt? You be the judge.
Acknowledgments: Written in 1996 by Max Traweek, Susan Wardroup, Jay Williams and E.L. Young. Maps and graphs by Max Traweek. Field activities coordinated by Jay Williams and conducted by biologists and technicians of the Texas Parks and Wildlife Department Wildlife Division, Bob Cook, Director.
Breeding Success and Fawn Survival
In some Texas circles, you still hear people talk about the "old barren doe" that lives in a certain pasture. This train of thought blames poor fawn production on the idea that many older does do not get pregnant. In reality, if the doe isn't bred during the first estrous period, she will be receptive again in 28 days. This explains the high breeding success in white-tailed deer even when bucks are scarce. We found that on the average, 92 of every 100 does sampled in the state were pregnant. The western part of the state was in a drought during much of the study. In the Trans-Pecos the number of bred does was the lowest. There the breeding rate dropped to only 81 percent (81 of 100).
White-tailed deer are known for producing twins. Statewide, over half of the does examined had twins. Triplets were not common, and the occurrence of triplets was less than two percent. Quadruplets didn't show up in the study. There were more male fetuses than female fetuses. Males represented 56 percent of the unborn fawns over the three years of the study.
An average sample of ten does had 15 fawns, or 1.5 fetuses per doe. In some parts of the state, though, deer numbers build up slowly. Failure to breed is not a problem, so where do the fawns go? Life is full of dangers for a fawn, and food and cover (the fawning habitat) is the difference in living and dying for fawns. In many parts of the state, predation is severe unless there is adequate hiding cover for young fawns. Imported fire-ants are a problem for fawns in heavily infested areas, but their impact can often mask the real problem. Adequate nutrition is often limiting, and if fawns make it past fire-ants and predators to weaning, they still face the challenge of finding food and cover.
Fawn survival depends primarily on habitat quality. Malnutrition and associated problems are probably responsible for poor fawn survival in much of the state. Dry conditions aggravate the problem of inadequate food. "Empty belly disease" is the most limiting factor on whitetails in Texas. Delayed breeding could cause fawns to be born late, which would be a disadvantage on ranges where food is scarce.
The Early and Late Ruts
What about the early and late ruts? Hunters and outdoor writers often talk about the rut being early or late. In Texas, at least, the breeding season for white-tailed deer is fairly predictable from year to year. Within a specific area, habitat conditions not only affect fawn survival, but can affect thetiming of breeding. A doe in poor condition or a young doe may not breed until late in the season. A doe may be attractive to bucks for about five days, but may be willing to breed for a period of only 24 hours. If the doe is not bred during her first cycle, she will generally come into heat again about 28 days later.
In areas where there are few bucks, a doe may not encounter a buck when she is first receptive and may not be bred until one of her later cycles. A hunter, landowner or biologist who sees the late breeding activity may be convinced that there was a late rut. On the other hand, those who see does attended by bucks in the early part of the season believe there was an early rut. This helps explain the wide variety of opinions on the timing of the rut during a particular year.
"Hunter chronology" has a lot to do with the perceived timing of the rut. Traditionally, hunters are more likely to be afield during cool weather. They will usually be out in force with the onset of the first weekend norther during the deer season. When there are many observers spending time in the field it is more likely that breeding activity will be noticed.
Bucks, like hunters, have a tendency to move around during cool weather. Bucks with hardened antlers are ready to breed and are looking for a willing doe. More movement means more opportunity to encounter a receptive doe. This increased movement helps give rise to the idea that cold weather causes the rut. However, this theory is disproved by white-tailed deer breeding in tropical climates.
We once thought that late fawning could be a problem in areas where survival was low and antlers were poorly developed. Newly weaned fawns on the range in late fall would have a harder time surviving. A lack of adequate nutrition at this time could affect future body and antler production. The study showed that very few fawns are born late in Texas. South Texas has the latest breeding period. Even there, fawns are born before August and are weaned by October.
The Rut by Geographic Areas
Clickable eco-regions map for breeding dates
Biologists who designed the study knew there were distinct rutting periods in different parts of the state. They picked 16 study areas which were typical of the different ecological regions. The areas represent north-south or east-west distinctions. Read the descriptions and look at the map to locate your area of interest. We list the earliest and latest dates for breeding in each ecological region and a "peak" breeding date for each study area. The graphs show the percent does bred during weekly periods throughout the breeding season.
Gulf Prairies and Marshes
The earliest whitetail breeding in the state occurred in this ecological region. Breeding occurred in the period August 24 to November 25. There were two study areas: the northern study area had a peak date of September 30, while the southern area was a month later with an October 31 peak breeding date. Does showed a 92 percent breeding success and 1.6 fetuses were found on the average for each doe sampled. The majority (90%) of the fawns would have been born by May 10 in the northern area and by June 6 in the southern area.
Post Oak Savannah
The conception dates for does in this region ranged from September 30 to January 16 during the study period. Two study areas were used. The peak breeding dates for the central and southern portions were almost identical. The peak dates were November 10 and 11, respectively. Does showed a 92 percent breeding success and 1.7 fetuses were found on the average for each doe sampled. The study shows the majority (90%) of the fawns are born by June 17 in the central area and by June 26 in the southern area.
Most breeding activity happened from October 21 to January 5. Peak breeding dates were November 22 in the northern portion and November 12 in the southern part of the Pineywoods. Does showed a 96 percent pregnancy rate and averaged 1.7 fawns each. The majority (90 %) of the fawns are born by June 29 in the northern area and by June 19 in the southern area.
Most does were bred from October 8 to December 30 in the three years studied. Study areas showed a peak date of December 3 in the north and November 20 in the south. The Rolling Plains had the highest incidence of pregnancy, with 97 percent. Biologists found an average of 1.7 fawns for each doe examined. The majority (90%) of the fawns are born by July 2 in the northern area and by June 26 in the southern area.
Conception dates for this region ranged from as early as October 9 to a late date of January 30. The Edwards Plateau, Texas' highest deer production region, was divided into three areas for the study. The eastern part had a peak breeding date of November 7. Peak breeding for the central portion was November 24, and the western area had a peak date of December 5. An average of 90 percent of the does were bred and the average number of fetuses found was 1.3 per doe. The majority (90%) of the fawns are born by June 14 in the eastern area, June 26 in the central area, and by July 13 in the western area.
Representing the north-central part of the state, conception dates in the Cross Timbers and Prairies were as early as October 13 and extended to December 17. In the northern portion of the region the average breeding date was November 15. The average breeding date in the southern part was November 17. Biologists recorded an average of 1.7 fetuses per doe and 95 percent of the females had been successfully bred. The majority (90%) of the fawns are born by June 15 in the northern area and by June 20 in the southern area.
Conception dates in the Trans-Pecos ranged from as early as November 4 to as late as January 4 during the 3-year study. The peak date of the breeding season was December 8. This ecological region experienced drought conditions during the last two years of the study. The resulting poor nutrition was reflected in the observed reproductive rates. Only 81 percent of the does were pregnant and the average number of fetuses was a low 1.0 fetuses per doe. The majority (90%) of the fawns are born by July 16.
South Texas Plains
South Texas had the latest rut in the state. Breeding dates ranged from November 9 to February 1 during the three years. In the eastern part of the area the peak breeding date was December 16, while in the west it was December 24. The pregnancy rate was 95 percent and there were 1.5 fetuses for each sampled doe. The majority (90%) of the fawns are born by July 19 in the eastern area and by July 25 in the western area.