UVALDE Supplemental feeding of white-tailed deer helps produce trophy bucks, but it can also mean trouble for ranglelands, according to Texas Agricultural Experiment Station research conduced in Uvalde.
One of the goals of a year-long study at the Harris Ranch in Uvalde was to find out if supplemental feeding of white-tailed would affect rangeland due to overgrazing of forage plants near feeders, said Dr. Susan Cooper, wildlife scientist and lead researcher for the study.
“To test this, we divided the ranch into six areas and provided supplemental feed year-round in three of the areas, Cooper said. “No supplemental feed was provided in the other three areas, which were used as control areas.”
Animals feed more selectively when food is abundant, said Cooper. Research has shown vegetation type and quantity can be affected by animal foraging patterns and intensity.
“Previous studies focused on supplemental feeding of deer during winter, so little was known about the effect of year-round supplementation,” Cooper said. “Since the current national trend is toward intensive management of native hoofed animals, such as year-round supplemental feeding of deer, we felt we needed to reflect that in our research.”
Year-round supplementation is well established on many Texas rangelands where white-tailed deer are closely managed to produce trophy bucks, she said.
“Deer receiving supplemental feed still continue to browse on native vegetation and increase their diet selection by concentrating on higher-quality plant forage species,” Cooper said. “We deduced that forage use by deer would be most evident close to location where the supplemental food was being dispensed to the deer.”
Cooper and her team established feeding centers in the middle of each of the six areas of the ranch to attract and trap deer with foraging ranges that included the area near the feeders.
Twenty-four adult deer were trapped and fitted with standard radio-telemetry collars.
“Following the capture of the deer, we randomly selected three areas and placed a permanent free choice’ gravity feeder at the center of those areas,” Cooper explained. “We used shelled corn instead of alfalfa or grain-based pelleted rations because this was the supplemental feed the deer were used to receiving at this ranch.”
Some supplemental food was provided in the control areas from October to mid-January in preparation for and during hunting season, but no data were gathered during that time.
Deer location was plotted by simultaneous time recordings between two sites, along with supplemental readings from other locations whenever possible, Cooper said.
“We compared the distribution of supplemented and non-supplemented deer within their home range areas,” she said.
The “home range” is the entire area an animal uses for feeding, breeding and other normal activities, Cooper noted.
While some of the deer lost their collars and some collars didn’t work, adequate sample sizes were obtained from eight does and six bucks. Home ranges were analyzed across seasons.
The browse utilization analysis was confined to three palatable plant species in the areas: partridge pea, lead-tree and guajillo. Plants used were raised from seed in separate pots under greenhouse conditions, and seedlings were placed at various distances up to 100 yards from each feeder and center of each control site. To avoid rabbit grazing the seedlings had to be placed in raised groupings.
“The fate of the seedlings was recorded as either browsed, dead or gone,” Cooper said. “Gone meant there were no additional seedlings available to replace the plant after it had been browsed. Each plant species and season was analyzed separately.”
Researchers observed browsing pressure on the seedlings increased with proximity to the feeder.
“Even in spring, when there was fresh, green vegetation throughout the area, seedlings in the arrays near the feeders were more likely to be grazed than seedlings in the control areas,” Cooper said.
Researchers concluded that providing shelled corn as supplemental feed had little effect on the home range size for the deer, mainly due to their having to travel widely to locate water and shade. However, feeding activity seemed to be more concentrated near the feeders.
“We saw that when supplemental feed was available to white-tailed does, much of their activity became concentrated into a smaller core area,” Cooper said. “But unlike the does, there was no evidence that bucks with access to supplemental feed concentrated their activity in a similar way.”
However, evidence of browsing on the seedlings showed all the deer in the study concentrated their foraging around sites where supplemental feed was available. This was true even when there was ample green forage material throughout their habitat.
“This means there is the potential for over-browsing of palatable plants near feeders and the failure of seedlings to establish,” Cooper said. “That may lead to zones of forage depletion around the feeders. So we must caution against long-term supplemental feeding in fixed locations because of the potential for range degradation.”
Landowners who provide supplemental feed to deer should observe the level of browsing on favored plants near feeders, Cooper said. If heavy use is noticed, feeder locations should be altered periodically to avoid possible forage degradation near them.
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