By Colleen Schreiber
KINGSVILLE A few years ago the Caesar Kleberg Wildlife Research Institute, Texas A&M Kingsville, and the Texas Parks and Wildlife Department conducted a survey of wildlife operations on South Texas ranches. The objective was to collect information about land and wildlife management practices and harvest and biological information about white-tailed deer. The information was collected during 1996 and 1997, which were dry and wet years, respectively.
Dr. Fred Bryant, director of the Kleberg institute, presented an overview of that survey at the recent South Texas Wildlife Conference here.
The South Texas survey included data from 187 ranches or leases involved in white-tailed deer hunting. Those ranches represent only 10 percent (1,686,732 acres) of the actual habitat in South Texas. The number of counties considered in South Texas was 29. The actual number of counties responding was 21.
Bryant stressed that it was not a scientific survey, but rather a survey sent to specific mailing lists.
"The data may be biased," he told listeners, "because of the lists used. Also, some of the responses may show an interaction or carryover effect of several practices. For example, while some who used food plots showed a positive effect, it is most likely that those who use food plots also control their deer herds, practice supplemental feeding, use improved harvest strategies, and incorporate good livestock grazing practices," he concluded.
Only 42 percent, 78 of the 187 respondents, reported taking a 140 Boone & Crockett buck or greater.
"The ones that did not report a 140 B&C buck either did not want the information known to us or they did not harvest a 140 B&C buck," Bryant said.
On the 78 ranches that harvested a 140 B&C, the bucks were harvested at a rate of one for every 11,829 acres in the dry year and one for every 6245 acres in the wet year. He pointed out that acreage of the ranches that did not report taking a 140 B&C buck were included in the calculations, and therefore the harvest rate is likely distorted somewhat.
Respondents took 133 percent more 160 B&C bucks in the wet versus dry year; 54 percent more 150-159 B&C bucks and 33 percent more 140-149 B&C bucks.
At least 81 percent of the respondents estimate deer density, Bryant said. As for deer weights, combining a wet and dry year, heaviest bucks weighed on average 156 pounds while the heaviest does averaged 95 pounds. The average weight of the heaviest bucks harvested was superior in western South Texas than in eastern South Texas, independent of the year or management practice, Bryant noted. Heaviest bucks in western South Texas were 14 pounds heavier than bucks in the eastern part of South Texas.
"This could be due to lower deer density, habitat conditions and/or management practices," he told listeners.
The number of acres per harvested buck was calculated by averaging the rates of harvest from each ranch or lease. Combining years, a sample of 4860 bucks was reported for this survey. Bucks in general were harvested at a rate of one per 613 acres in western South Texas and one per 617 acres in eastern South Texas. Acres per harvested buck scoring at least 140 gross B&C was 1890 acres in the western part and 2534 acres in the eastern part of South Texas. Does were harvested at a rate of one per 522 acres and one per 456 acres in western and eastern South Texas, respectively.
In addition, bucks harvested on high-fenced ranches were on average 12 pounds heavier than bucks harvested in ranches with no high fence, 14 pounds heavier during the wet year. Bryant attributed much of the difference to management behind the high fence, for example the ability to control deer density, and not to the fence itself.
Fencing, however, did not affect doe harvest weights.
"This is probably because does are randomly harvested while bucks are harvested based on larger antlers and body size," he explained.
Fifty-six percent of those responding to the survey indicated that they plant some form of food plots, and of those, 41 percent said they plant both summer and winter food plots. Those who planted food plots did so at a rate of one acre of food plot for every 188 acres of land.
As for supplementation, about 89 percent of the acreage covered by the survey employed some kind of feeding program. No effect of protein supplementation was observed on weights of heaviest does, while a slight effect was found for the bucks, Bryant said. Bucks supplemented with corn and protein were nine pounds heavier than the ones fed only corn. Also, the effect of corn plus protein supplementation compared to corn alone was more pronounced for buck body weights in the wet year than in the dry year. Bucks were 13 pounds heavier in the wet year when fed protein.
"This might be due to nutrient supplement being used by deer for maintenance in a dry year versus building body mass in a wet year," he explained.
In the dry year, the harvest rate of 140 B&C bucks was improved when corn and protein were supplemented compared to those ranches where only corn was supplemented. This effect, however, was not noticed in the wet year.
"We believe that is because in a wet year, native forage is likely providing a higher percentage of nutrients needed to enhance antler growth. This reduces the need for and/or use of protein supplements."
Bryant explained that contrary to popular opinion, feeding protein or supplement complicates management.
"You will have to intensify harvest because you will most likely have higher fawn crops and adult survival," he pointed out. "Thus, you must be committed to harvesting many more deer each year to keep the population in check. Also, younger deer will likely reach heavier body weights, and this could cloud culling decisions because a two and a half year-old deer might be the same size as a four and a half year-old deer."
Another area of flawed thinking in regard to supplementation has to do with carrying capacity. Supplementation, Bryant stressed, does not increase carrying capacity of the habitat. Supplementation can increase deer density, but carrying capacity and density are two totally separate terms. The only way to increase carrying capacity is to increase the native plants available to the deer. In fact, he noted, feeding protein can increase the feeding pressure by deer on preferred native plants, and unless the population is carefully controlled, those preferred native plants will likely disappear. Bryant also questioned whether providing protein and food plots is economical.
Livestock grazing, Bryant told listeners, positively affected the average weight of heaviest buck harvested, and the effect was more dramatic in the western part of South Texas, where they were 20 pounds heavier with livestock grazing. Doe weights were not affected by livestock grazing.
More than half of the respondents used rotational grazing, which corresponded to more than 54 percent of the land covered by the survey. The survey indicated that rotational grazing of livestock was better for deer than continuous grazing. Average weight of the heaviest bucks under rotational grazing was heavier by 10 pounds compared to the ones under continuous grazing. Again, no difference was observed in doe weights. Though livestock grazing appeared to be positive for white-tailed deer, the speaker recommended conservative stocking rates.
The harvest strategy data, Bryant said, was mixed, and therefore the results of the survey were inconclusive regarding which harvest strategy to use.
Almost 50 percent of the respondents receive professional advice from TP&W, and 85 percent of the respondents collect and record harvest information. About 82 percent of the respondents indicated they harvest mature bucks and 47 percent harvest spikes. Relative to culling at a certain age and excluding spike harvests, seven percent of the respondents try to cull bucks primarily at 2.5 years of age and older, while 18 percent wait to cull bucks primarily at 3.5 years of age and older.
Only 21 percent of the respondents indicated that they have any kind of active predator control. In general, then, Bryant said, predator control had little impact on the results of this survey.
Copies of the survey are available from the Caesar Kleberg Wildlife Research Institute or from TP&W.
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