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Abnomality? Genetic defect?

AU grad student seeks answers

Abnomality? Genetic defect?
Never mind the brow tine, this buck at the Auburn deer lab is considered a spike-on-one-side (SOOS) buck. Auburn graduate student Gabe Karns is soliciting hunters to send in the skull plate and antlers of SOOS bucks to further a study being done to determine the causes of the malformed antlers.

By David Rainer
Alabama Dept. of Conservation and Natural Resources

Anyone who has hunted deer in Alabama has pondered the question when a buck walks out sporting a fine antler with multiple points on one side and a puny spike or much less desirable antler on the other side. Many hunters, who shoot the deer as a cull, blame that abnormality on a genetic defect, but Gabe Karns, a graduate student at Auburn University, hopes to determine if that theory holds water.

"This may be the simplest research that's ever come out of Auburn University, but there's nobody who hunts who isn't interested in the results," Karns said. "If you've hunted much, you've seen a buck like that. You sit there in the stand and wonder, ëDo I need to shoot that buck or will he come back next year and be better?' This is just simple research designed to educate people on one of the mysteries of deer."

The Alabama Division of Wildlife and Freshwater Fisheries (WFF) is cooperating with Karns to encourage hunters to provide antlers and skull plates from harvested bucks with a spike on one side (SOOS) for inclusion in the study. SOOS bucks have one normally formed antler on one side and a spike or a forked prong on the other side.

Karns became interested in the SOOS phenomenon when he was doing research for his master's degree at North Carolina State University. One particular study area, Chesapeake Farms on the Eastern Shore of Maryland, had a significant issue with adult buck mortality.

He put GPS tracking collars on a number of the SOOS bucks and was surprised to discover that about half those collared bucks failed to make it to the next season.

"I lost almost 50 percent of them to natural causes," Karns said. "When we had several of them necropsied, a brain abscess came back as the culprit time and time again. Nine times out of 10, if we darted a deer with a spike on one side, you could just about put a $20 bill down that that deer was going to die of a brain abscess."

It was determined that the abscesses were caused by bacteria prevalent in that deer herd in Maryland. In the meantime, Karns moved to Auburn University to work on his doctorate with Steve Ditchkoff, associate professor in the School of Forestry and Wildlife Sciences.

Karns said a magazine article on SOOS bucks came to the conclusion that hunters pretty much lumped those bucks into a catch-all category of genetic cull buck.

"That designation as a cull buck has become a pretty good excuse to take the safety off and pull the trigger," he said. "There's nothing wrong with shooting those bucks. But then the hunter comes back to the camp saying, ëOh, I really did our deer population a favor by taking that buck out of the herd. He obviously had bad genes.'"

Karns said the brain abscess theory merged with Ditchkoff's opinion that SOOS bucks are rarely a result of a genetic defect. As part of his dissertation work, Karns said he can advance the research if he comes up with enough SOOS samples.

Last year Karns asked numerous hunters to save the skull caps and antlers from their SOOS bucks. However, hunters overestimated the number of SOOS bucks in their herds, and Karns ended up with far fewer samples than needed.

"This fall we've made a much bigger push," he said. "We want to look at as many as possible. In a perfect world, I'd have the whole deer and have a veterinarian perform a necropsy to look for old injuries or other causes.

Obviously, we can't do that.† Whatever percentage of spike-on-one-side bucks that we can attribute to physical injury, no matter how we get to that number, we're going to underestimate it. With just the skull plate and antlers, we're not going to be able to determine if he broke his leg two years ago."

A physical injury can sometimes lead to malformed antlers when the deer's growth resources are diverted to repair the injury.

"By the time a deer was three years old, close to 80 percent of the time we could point to a symptom, whether it be a deformed pedicle or broken left leg or whatever, as to why he had a goofed-up antler," Karns said.

With the Auburn deer lab in Camp Hill and several other captive herds, Karns said there are a good number of ear-tagged bucks that will be used to track antler development, as well.

From the skull plate, Karns said there are a couple of clues that can be determined. One is the bacteria that is the culprit with brain abscess. The skull plate of an infected deer will have pitting and erosion around the pedicle. The bacteria causes the abscess, which puts pressure on the brain. When it ruptures, the animal dies.

The good news is that Karns has not found evidence of that strain of bacteria in the deer herd in Alabama.

"I sampled for it in Alabama," he said. "I sampled 10 live deer from a site near Union Springs and did not get a single hit on that bacteria."

Because of the absence of that bacteria in the Alabama deer, Karns said the focus of the research can now be done in the areas where there is a high prevalence of SOOS bucks.

"There may be hot spots around the state," he said. "There may be bacteria in some of those areas. That's thin ice to skate on right now, but it may help us start to explain why 30 to 40 percent of one deer herd has spike-on-one-side bucks, while the place I hunt, 40 miles down the road, I've seen one in four years.

"Dr. Ditchkoff's theory is that rarely is a spike on one side attributed to a genetic defect. What I'm trying to do is to put a number to his premise, like yeah, in 85 percent of spike-on-one-side bucks there is a physical attribute you can point to and say with a high degree of certainty that this deer was a spike-on-one-side because of a damaged pedicle or a broken left leg last year."

Karns said he can't eliminate genetics as the reason for an SOOS buck, but he thinks simple logic suggests that it's not, that other factors are involved.

"The guy coming back to camp and saying he did the deer herd a favor by shooting that buck to keep him from spreading bad genes ñ that's probably not true," he said. "Basically, what we're trying to do is to understand whether that statement holds much water. That's sort of the background we're using."

Karns said he would like to get at least 150 heads this fall for his research. He has already recruited several hunting lodges, Wildlife Management Area biologists, large landowners, as well as Lann Wilf and William McKinley, neighboring district biologists with the Mississippi Department of Wildlife, Fisheries and Parks in east central Mississippi.

Although the program is premised on spike-on-one-side, Karns said any deer that has a malformed antler on one side would be a valid sample.

"If it's one of those bucks where you say if it just had the other side he'd have been a really nice deer, send him to me and I'll take a look at him," he said. "Even if he does have a main beam and a couple of other sprouts, eight out of 10 times, you will find a damaged pedicle. The deer just can't pump the same nutrients out of a damaged pedicle."

Contact Karns at grk0002@auburn.edu for information on how to participate in the SOOS collection process. Skulls should be cleaned with no hide or significant amount of tissue remaining. European-style skulls and skull plates with at least one inch of bone surrounding both pedicles in all directions are acceptable samples. If the hunter wants the antlers back, they will be returned after examination.

Alabama hunters are allowed to harvest three bucks a year, one of which must have at least four points 1 inch or longer on one antler. Harvesting an SOOS buck will count toward the three-buck limit. Visit http://www.eregulations.com/alabama/ for a complete list of hunting regulations.

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