March 16, 2011
As long as there have been whitetails, there have been bears, cats, canines and humans to eat them. So what role do predators play in modern deer management, and can natural predation have an adverse effect on a deer herd, especially one geared toward producing mature bucks for human harvest?
It's not a question that science has ignored. Whitetail predation has been the subject of numerous studies across the country, and the results were the same: Predators eat whitetails. But the degree to which predators can negatively impact a herd or management program varies wildly, depending on a host of factors. Is the "predator problem" all hype? Or should managers take serious and expensive steps to limit their toll? I talked with an old friend, one uniquely qualified to answer my questions, in attempt to answer this vexing management question.
I met Dr. Mick Hellickson almost a decade ago on a hunt at South Texas' fabled King Ranch, where he worked as a biologist. Hellickson had two passions in life -- deer hunting and deer research. As a research scientist, Hellickson spent much of his time studying the lives of mature South Texas bucks. Hellickson has since moved on, starting a successful consulting business, Orion Wildlife Management Services. His research background and varied client list -- properties are spread across the country and client pockets range from deep to not-so-deep -- made him the perfect source to answer the predator problem question.
Our conversation really centered around one animal, the coyote. Sure, there are numerous other predators, but the coyote probably has the most impact on deer herds and certainly is the most widely distributed. Mountain lions take their fair share of deer, and so do grey wolves where their ranges overlap with whitetails. Bobcats and black bears are also big-time whitetail predators. Some of these critters are considered big game species, others are simply known as furbearers and some are even listed as endangered species, so opportunities to manage them are limited. But coyotes, in most locales, are considered varmints, and, thus, the gloves can come off in terms of control.
When Hellickson moved to South Texas in 1988 as a graduate student, his first task was to complete a three-year research project that looked at post-rut buck mortality due to predators. In one year, Hellickson removed 100 coyotes and 30 bobcats on two 5,000-acre treatment areas with leg-hold traps and M-44 sodium cyanide guns. In the previous two years, another graduate student had removed more than 300 coyotes from the same two areas. Bucks fitted with radio collars were closely monitored on both treatment areas, as were deer on two adjacent parcels not subject to any predator control. When the mortality sensors beamed out a death signal, Hellickson went into the kill site to try to determine the cause of death.
"We lost five bucks on the control area and two on the treatment area over three years," Hellickson said. "You have to get results that are statistically significant, and the sample sizes were just too small to show a statistical difference. We couldn't state that trapping and controlling predators made a difference."
But long after the paper was published and added to the dusty reams of whitetail research, the real-world results of the intense predator control program stuck with Hellickson.
"The trapping program saved three radio-collared bucks and who knows how many bucks without collars," Hellickson said. "On a ranch that is commercially hunted, those three bucks could have grown into animals worth $20,000 each, and that made the control program worth the effort."
Many hunters are skeptical that a 30-pound coyote can kill a mature buck. Hellickson and other researchers have witnessed it numerous times.
"Bucks, on average, lost 30 percent of their body weight during the rut," Hellickson said. "Their energy reserves are low and their late-winter and early-spring home-range sizes are reduced. Bucks are moving very little and low energy reserves make them highly susceptible to coyotes. The post-rut period for bucks is the "pre-rut" period for coyotes, and they are in packs, hunting in groups. This allows them to take mature bucks."
The bulk of Hellickson's clients are in South Texas, and many of those ranches are high-fence properties. This gives managers a leg up on coyotes and other predators. The fence serves as a ready-made, easy-to-access trap line for snares and leg-hold traps. Find a hole under the fence and set a trap or snare.
A biologist or trapper can easily set, service and maintain enough traps and snares to make a big dent in coyote populations since most perimeter fences have a perimeter road a few feet away. Without a high fence, predator control is a much more labor intensive and expensive proposition.
"It takes a long line of traps that requires a lot of labor to maintain," Hellickson said. "It would really take a full-time trapper to make a difference. Most ranches I work with can't afford that kind of labor."
Incidental hunter kills of coyotes or bobcats are not common enough to make a big difference. Exceptional predator hunters are obviously more effective, but a well-run trap line probably offers the most bang for the buck.
"I don't know what the exact threshold is, but killing coyotes randomly when hunting is not going to have any impact," Hellickson said. "Removing a handful is not going to do it. A manager has to implement an intense trapping program to have a measurable effect."
Obviously coyotes and predators in general do not limit their take to solitary, worn-down bucks. Fawns are the other venison choice on the menu and probably the preferred snack between the two. And this is where predator control has the biggest impact.
"The biggest reason to control predators is to increase fawn survival," Hellickson said. "On ranches where I recommended predator control and it's done right, we count more fawns during our fall helicopter surveys."
Dr. Grant Woods and Dr. Karl Miller, both noted whitetail researchers, recently completed studies in South Carolina and Alabama that mirrored the results of studies in South Texas. In fact, almost a dozen studies across the country over the years have looked at fawn predation, and all showed that if predators are controlled, fawn survival rates increase, in some cases doubling from 30-40 percent to 60-80 percent.
A study in Hellickson's home state of Iowa showed that 30-35 percent of fawn mortality could be chalked up to coyotes. They were the leading cause of fawn deaths in a state where coyote densities are relatively low. Coyotes, predators in general, probably sit at No. 3 on the list of factors that determine population density behind hunter harvest and weather.
"This is obviously a huge factor for my management recommendations, since it often means twice as many fawns are surviving to the fall," Hellickson said. "The result is you get more buck fawns to survive to the yearling age-class the following year. Just do the math. Having twice as many yearling bucks is having a huge, positive impact on a deer herd."
Of course, having more deer can be a double-edged sword, especially in locales where deer herds are chronically overpopulated. I hunt a farm in the Georgia piedmont that has 60-70 deer per square mile, and we often joke that the coyotes are doing us a favor, since we are rarely able to meet our doe harvest quotas. If we could only teach coyotes and other predators just to eat doe fawns, everyone would be happy.
"Limiting predation will probably drive herd numbers beyond the carrying capacity of the habitat," Hellickson said. "You will certainly have to increase doe harvest. To some folks, it's a positive because they get to kill more deer. To others it's a negative because they have to kill more deer."
The advantage, of course, is that human hunters can be very selective about the deer they kill. Coyotes don't have the same luxury.
The ability to manage predators -- and a deer herd, for that matter -- is often limited by time and money. But managing one certainly has an effect on the other. If hiring a full-time trapper is not in the cards, managers can mitigate the effect of predators with habitat and herd management. For Hellickson, trapping and intensive hunting are tough propositions on his farm in Iowa, since he lives in Texas.
"One of the first things we did in Iowa was to increase native warm-season grass cover," Hellickson said. "This provided more habitat for fawns to hide in and was the most efficient and effective way to increase fawn survival."
Balancing sex ratios leads to a shorter, more intense rut. Hunters love to see the chasing and fighting, but the biggest advantage takes place in May, when few hunters are in the woods to witness the birth of fawns.
"A narrower breeding season window means that more fawns hit the ground at the same time," Hellickson said. "This swamping effect means more fawns will survive."
All properties, even those across a river or highway from one another, are unique and all require their own prescription. Predator control might be the most critical factor holding a ranch back in terms of mature buck production, or it might sit on the list below habitat or hunter management. But you can count on predators to be a factor.
"I respect the coyote," Hellickson said. "The're intelligent and have survived all these years after being intensively targeted for harvest.
"There is a place for coyotes in the deer world, but managers interested in intensive deer management have to consider them a factor. The more you manage them, the better the herd."