Publisher
Colleen Schreiber, Livestock Weekly
KINGSVILLE — At the recent South Texas wildlife seminar, veteran deer researcher, Dr. Charlie DeYoung, discussed deer management techniques, both common and new, influenced by South Texas research.
He started off with capture techniques. The net gun is what is primarily used today for capturing deer though the technique has evolved considerably from the early day box traps.
“There were thousands of deer trapped on the Aransas National Wildlife Refuge and on the King Ranch in the late 1940s and 50s using box traps,” said DeYoung. “They were used to translocate deer throughout Texas and other states and even other countries.”
The dart gun is another tool though he said it’s used primarily in deer pen settings. Also the drop net is used primarily in capturing deer in urban settings. This technique is known to cause the greatest post capture mortality.
In the late 1970s, for a couple years running, researchers chased deer with a helicopter into a pond and then roped them, DeYoung told participants. Then came the drive net in about 1981, which essentially was a fence with temporary supports. A helicopter was used to run the deer into the net and people were scattered out along the net to tackle the deer. The net was developed in New Mexico and first used in South Texas on the Chaparral Wildlife Management Area.
“It came to Cotulla on a Greyhound bus in about 20 cardboard boxes,” DeYoung recalls. “There was a learning curve.”
Then in 1985 came the net gun. Today there are many commercial companies that do this kind of work. It’s one of the safest capture techniques for the deer with only about a two percent mortality rate, which DeYoung said is a bit surprising because the method appears to be pretty rough on the deer.
DeYoung also pointed out that before the drive net and the net gun techniques came along it was difficult to really get a handle on the age structure of a lot of the deer population in South Texas.
“We’d fly a helicopter survey and we’d see a bunch of young deer, a bunch of middle-sized deer and a few classes of trophy deer, but we didn’t realize a lot of these middle-sized deer were actually mature deer until we started catching large numbers of them with these techniques,” said DeYoung.
Now these methods are largely used today for Triple T permits, for deer management permits and the like.
He also briefly discussed the various survey methods used in South Texas including spotlight counts, helicopter surveys, camera surveys and more recently drone surveys. CKWRI has done some research on spotlight counts and because of the high count variability, its best to do several counts and average the results, DeYoung said. He added that the way they used to estimate the area being surveyed was they would measure perpendicular to the transect line. The long and the short it was “really biased” and resulted in an overestimate.
Spotlight counts don’t work all that well in dense brush, he said. Additionally, sometimes the herd composition data is difficult to interpret with spotlight surveys. Research also showed that it’s better to count deer after midnight, which few people want to do.
There has also been quite a bit of research done on helicopter surveys. Again, what researchers found is high count to count variability. For the most part only running deer are seen; seldom seen are the stationary deer. Thus the deer that are bedded down are likely to be missed. Different times of the day and different conditions can also skew counts. In fact, DeYoung told the group that helicopter surveys have less than a 50 percent accuracy rate. It’s a bit better if winter counts are done, he said.
DeYoung also noted that sex ratios, the buck to doe ratios, are unbiased, though they may be variable from count to count. Also, the aged buck encounters are typically unbiased as well. However, fawns are undercounted by as much as 30 percent. Overall, DeYoung said he likes to use a three year running average to take out some of the count to count variability when using this surveying technique.
Camera surveys are a good censusing method for smaller properties. He suggested working with the local TPWD biologist to calculate a population estimate based on camera survey pictures. He added that a pretty good camera density is needed to get a good estimate. DeYoung also told participants that camera surveys can be more accurate than a helicopter survey even when done correctly it’s an undercount of the actual population. Additionally, camera surveys done over bait or feeder sites will be biased towards bucks, meaning there will be more buck pictures than other classes of deer. Also, if the camera is set up over a fenced feeder site with hog panels, for example, fawn pictures will be particularly limited.
Research on the use of using drones for deer population counts is just emerging, DeYoung said. What is known so far is that off the shelf, drones are not very useful at all. He said a drone with a thermal camera which can cost tens of thousands of dollars works best. Also, the FAA may require a pilot’s license to operate a drone.
DeYoung said that one of the real advantages of a drone census survey is that unlike spotlight and helicopter counts, drone survey counts are repeatable because the deer aren’t running. Overall, he said it is a promising technique though more research is needed to really determine the best way to conduct a drone survey.
Turning then to supplemental nutrition, DeYoung said deer enthusiasts use a variety of methods, everything from food plots to pelleted feed. He pointed out that cottonseed has become particularly popular of late. It is a good supplement though it has the chemical gossypol. In livestock, gossypol has been proven to reduce a bull’s sperm count. Thus, those who feed cottonseed year round to their deer often quit feeding it during the rut.
“I don’t worry about it too much,” DeYoung told the group. “I feed it year-round on our ranch, and I don’t see any particular problems with it.”
Researchers did quite a bit of work a number of years ago on the use of food plots in South Texas. He noted that they’re particularly difficult to grow in South Texas, particularly south and west of Cuero where it’s drier and rainfall is more variable. He added that it is possible to grow them in the drier climes, but getting a food plot established really requires a lot of farming expertise and expensive equipment. The food plot needs to be fenced in the early growing stage.
A lot of people also feed protein pellets. DeYoung noted that while the deer need the protein, it is really the energy that is the more important component of the pelleted feed. Research has proven that feeding pelleted protein results in across the board increased deer productivity when implementing a comprehensive program.
“I’m not talking about putting out a few bags for a couple of months. I’m talking about feeding for months or year round.”
He suggested feeder sites at least every 200 acres or so are needed to adequately distribute the feed throughout the population.
Besides increased productivity, feeding pelleted protein has resulted in over 15 inches in average antler size of mature bucks, increases fawn survival and improved bodyweights.
Some of the downsides are that a lot of ranches don’t feed during hunting season or at least some of those months because they don’t see their mature bucks. He also noted that cattle, hogs and other nontargets can be a problem. Thus he noted that fencing is usually warranted, but he also reiterated fawn access then becomes an issue though there are ways to mitigate that.
Pelleted feed is expensive, it requires infrastructure. Plus, there are obviously associated labor costs.
Additionally, CKWRI research has shown that a comprehensive feeding program has a protective effect on preferred forbs.
“That seems counterintuitive,” said DeYoung. “What we think is going on is that most of these deer feeds have a lot of grain in them; they’re a ‘hot’ feed which causes some digestive issues for deer, so they end up eating a lot of rough forages to offset those congestion problems rather than eating some of the more preferred browse plants and forbs.”
He also told participants that deer performance varies with rainfall.
“During a drouth, deer performance will be better if there is a comprehensive feeding program in place but even when feeding there will be swings in fawn survival, antler growth and so forth,” DeYoung told participants. “The best performance comes with feeding plus habitat diversity.”
He also briefly discussed density dependence. In layman’s terms, more deer means less of the high-quality preferred foods therefore the deer’s performance declines and related to the deer density, that is density dependent. However, CKWRI research has also shown that especially in deep South Texas and the western portion of South Texas, deer populations have weak or sporadic density dependence. He noted that it’s likely lesser of an issue in the higher rainfall areas.
DeYoung also shared one of his pet peeves that being harvesting does in deep South Texas in October and November.
“These deer rut during December or late December and fawns are born in July, on average,” he explained. “If you kill does in October and probably November those fawns aren’t weaned yet.”
As for predation, coyotes are the primary problem when it comes to fawns. Bobcats will kill some fawns and occasionally an adult deer, but in general they’re not an issue. There are some mountain lions in the major river drainages in South Texas, which obviously kill some deer, but overall they’re not a big problem, he said.
Specific to coyotes he said that there was a lot of research done in the 1970s which suggested that coyotes have a significant effect on fawns mostly in the first month of life. Other studies, however, have shown little affect.
“The research record of coyotes killing fawns is a little spotty,” said DeYoung.
He also told participants that it’s difficult to take enough coyotes to actually make a dent in the population and have a positive impact on fawn survival.
“Coyotes are territorial,” he explained. “Removing those territorial animals just creates a vacuum for other coyotes so it’s an ongoing process and very difficult to make a difference.”
Though controversial, deer breeding is another tool that can’t be ignored because some deer enthusiasts are employing it. There is very little research, however, on the ranch effects.
“We hear about people adding 10 bred does or 50 bred does to a deer population of several hundred and that just has no effect,” said DeYoung.
There are some who have tried to shoot out their native deer herd under high fence and start over with breeder deer.
“That practice seems to have a significant effect on antler size,” said DeYoung. “It all depends on how much
artificiality you want.”
He added that there is a learning curve for these breeder deer, and it takes a couple of years for them to really get going if they survive.
“They have to learn to eat and learn how to survive,” he pointed out.
There is also the deer management permit which is essentially another piece of deer breeding that is pretty widely used in South Texas. Specifically, the practice enables one to put a pen-raised buck with up to 20 native does in a small pen for breeding. The adults and offspring are then turned out after a few months.
The Faith Ranch near Carrizo Springs has done quite a bit of research on this particular management practice.
That research shows that older age class deer are larger using this method.
Over the years there has also been quite a lot of controversy over spiked antler deer whether they should be culled and whether that culling does any good. Considerable pen research showed a gain by culling spikes.
There is also some field data now that shows spiked yearlings are smaller at maturity than forked antlered yearlings. However, DeYoung suggested that there is actually little gain.
“For one reason, if a property is not high-fenced, up to 40 percent of these spiked yearlings will disperse up to several miles away,” said De Young. “So your young deer are leaving, and your neighbor’s deer are coming in so it’s really hard to concentrate any genetic pressure.”
He also told participants that CKWRI’s long-term research on this topic has shown little genetic progress from culling spike bucks.
“Most of you probably don’t believe that’s true. Again it’s counterintuitive,” he told participants. “For one there’s only one sex with the trait so half or more of the population is not getting culled.”
Another reason is there are environmental effects.
“What you see is not necessarily what you get,” said DeYoung.
“Bucks with mediocre antlers may have genes for good antler growth and some of the big bucks don’t have genes for good antlers. Some may be affected by environmental conditions in their early growing stage, and some may not.”
Still another factor is that a lot of the bucks are doing the breeding.
“It’s not like with cattle where one bull is used to breed 20 to 25 cows,” he noted.
With deer there’s about 40 percent of the mature bucks doing the breeding, but there are a bunch of other bucks breeding including yearlings.
“Yearling breeding seems to be happening right in the peak of the rut,” DeYoung said.
There is also multiple paternity. Specifically, 25 percent or more of the fawn twins are fathered by different bucks.
Finally, DeYoung discussed deer aging. The primary aging tool that most use is the tooth replacement and wear technique developed by C.W. Severinghaus in 1949. The method tends to overage young deer and underage old deer, said DeYoung.
He shared some data of his own aging of several hundred live known aged deer. The level of accuracy falls off the older the deer gets, he said. Specifically, he aged the year and a half old deer by the replacement of the premolar accurately 100 percent of the time. The 2.5 year-old deer were aged accurately 84 percent of the time, but the accuracy really fell off after that and it continued to decline, DeYoung said.
A new research paper published last year focuses on using the first molar to do the aging. The deer grouped as two year-olds, three to five and six and older was about 70 percent accurate using this method.
“If interested in grouping deer into those categories, the accuracy of this aging technique is improved,” said DeYoung.
Another way of aging deer is the cementum annuli technique. It involves extracting a front tooth out of the lower jaw for laboratory analysis. The technique is similar to the aging of a tree using growth rings.
DeYoung said the technique is unbiased relative to the age and wear technique. However, he told participants this technique doesn’t work as well in South Texas as it does in the more northern states. Overall, it has the same accuracy as the age and wear.
He added that there may be an advantage to using this technique if there are several deer camps with different people with different abilities aging the deer and a more consistent process for aging is desired.
DeYoung wrapped up with a quote from former U.S. Defense Secretary, Donald Rumsfeld.
“There are known knowns; there are things we know we know. We also know there are known unknowns . . . ,” Rumsfeld said.
“We know that we need more information like I mentioned with drones, and then there are things we don't even suspect we don't know. The bottom line is more research is needed,” he concluded.