A recent study by Texas AgriLife Extension Service confirmed that it’s possible to exclude feral hogs from wildlife feeding stations without limiting access by white-tailed deer.
The study found fencing 20-inches high did not entirely exclude feral hogs, but that 28-inch or 34-inch fences were equally effective in completely excluding the invasive species without limiting access by adult white-tailed deer, according to Dr. Billy Higginbotham, AgriLife Extension fisheries and wildlife specialist.
A second phase of the study Nov. 5 through Dec. 3, 2009, largely confirmed the results of earlier tests conducted June 29 through July 28, 2009.
Higginbotham conducted both phases of the study at the Welder Wildlife Foundation near Sinton. He worked with Dr. Tyler Campbell, wildlife biologist and station leader at the U.S. Department of Agriculture's Wildlife Services-National Wildlife Research Center near Kingsville, and Duane Campion, AgriLife Extension agent for San Patricio County.
Higginbotham and Campbell enclosed deer-feeder sites with fences of three heights: 20 inches, 28 inches and 34 inches. All fences used six 16-foot-long panels, staked with steel T-posts and arranged in a circle around the feeders. During July and August, remote-sensing cameras, which were tripped by detecting motion, were used to record deer and feral hog traffic. The cameras recorded traffic before the fencing was erected and then for two weeks after, through late July and early August. The fencing was mounted on steel T-posts in 28-foot diameter circles around tripod-style deer feeders.
They constructed the fencing of crisscrossed galvanized steel wire, commonly called "livestock panels" and used by cattlemen to build corrals and working pens. For the high fencing, they used 34-inch by 16-foot panels. For the medium-high fence, they cut 5-foot by 16-foot utility panels in half lengthwise, which yielded the 28-inch high strips. And for the low-height fence, they ripped the same size panels in thirds to get 20-inch high strips.
As cost is a concern for most hunters, landowners and deer-lease operators, Higginbotham and Campbell considered materials and labor involved in construction. All things considered, the 28-inch- and 34-inch-high panels cost about the same, he said.
There were no added labor costs to split the 34-inch panels as they come at that height, he said. But to get two 28-inch panels involved splitting a 60-inch panel, so using six panels 34-inches high arranged in a circle around the feeder and secured with 12 T-posts seems the best management practice for both effectiveness and cost.
"Including T-posts and T-post clips, our high-, medium-, and low-exclusion fence material costs were $190, $187 and $142 per deer feeder, respectively," Campbell said. "If managers cut T-posts in half, these costs would be reduced. Additionally, our three-person fence construction crews were able to build one exclusion fence in approximately 45 minutes and this was consistent among fence designs."
At each site, they set up digital cameras that were automatically tripped by motion of deer, hogs or other large animals. They recorded the data from nearly 112,000 images during the summer trial and more than 75,000 images from the winter trial.
In both trials, all three fencing heights limited feral hog access, but the two highest fences excluded them completely. To a small degree, the 34-inch fencing and the 28-inch fencing limited some deer access as well, but the overall effect on deer traffic was minimal as they could easily jump the fences, Higginbotham said.
There were more visits to the sites by deer in the summer than in the fall, Higginbotham said. He said this was related to drought and its reduction on the deers’ natural food sources.
"From January through July, our study site received only 28 percent of its average normal precipitation for the period and available deer forage was reduced, which may have prompted deer to visit feeders at a greater rate," he said. "Nearly average normal monthly precipitation occurred from September through December on our study site, which increased available natural forage during our winter trial."
Studies of exclusion fencing by other researchers found that fawn visits to feeders were few and far between where there was fencing. During the summer phase of the trial, while the automatic cameras observed fawns with does, at no time did the fawns consume corn at the feeders, either before or after fencing was installed, they said.
During the winter phase of the trial, the cameras again recorded fawns with does, though at reduced numbers, probably because of the drought, Higginbotham said. Again, no fawns were recorded consuming corn, but he said it was unlikely a lower fence height would result in fawn feeding.
Higginbotham and other wildlife experts have said the lack of fawns at corn feeders is more likely due to "social interactions" among the deer.
"Even when fawns are plentiful, whenever bucks, does and fawns congregate around a deer feeder, the bucks are at the top of the pecking order, the does second and the fawns get pushed around by everyone else," he said. "Therefore, the fawns present may be under-represented on camera due to these social interactions."