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"Culling" in the deer-hunting sense is the idea that removing bucks with less-than-desirable antler characteristics for their age will increase antler quality of future bucks by changing the genetics of the population. To test this idea, Donnie and his co-researchers Dr. Charlie DeYoung, Ph.D. student Masa Ohnishi, and Dr. Randy DeYoung of Texas A&M-Kingsville and Dr. Bronson Strickland of Mississippi State University set up three areas on the Comanche Ranch for study. They included an "intensive" culling treatment area (3,500 acres), a "moderate" treatment (18,000 acres), and a "control" area where no culling would be performed (5,000 acres). Other than size, the three areas were similar in habitat and herd characteristics.
Each fall from 2006 to 2015, researchers used helicopter net-gun crews to capture bucks in all three treatment areas (this area of southwest Texas is virtually treeless brush country where aerial capture is feasible). Researchers estimated each buck's age based on tooth replacement and wear, collected a DNA sample, measured the antlers, and inserted a microchip PIT tag in the ear.
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These were the culling criteria used:
Intensive (3,500 acres): Yearlings with less than 6 antler points, 2-year-olds with less than 8 points, 3- to 4-year-olds with less than 9 points, and bucks 5 or older scoring less than 145 gross Boone & Crockett inches were culled.
Moderate (18,000 acres): 3- to 4-year-olds with less than 9 points and all bucks 5 or older scoring less than 145 gross Boone & Crockett inches were culled (the same criteria as the intensive treatment except no yearlings or 2-year-olds were culled in this area).
Control (5,000 acres): No culling at all. All captured bucks were evaluated, tagged and released.
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Intensive: Buck Population Crash
The stringent culling criteria in this area of the ranch resulted in predictably extreme culling. Each year, 85 to 100 percent of yearlings captured in this area met the culling criteria, even though DNA studies ultimately revealed that many of them had fathers that were not cull bucks.
"Culling yearlings with less than 6 points essentially crashed the buck population," said Donnie. "The intensive criteria equated to a 93 percent cull rate of every yearling we captured. When you add in natural mortality factors like predators and drought, we were basically removing recruitment. The population couldn't compensate through reproduction."
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Moderate: Zero Benefits
Without culling yearlings and 2-year-olds, the moderate treatment did not produce the negative effect on the buck/doe ratio that led to cascading effects on fawn birth dates in the intensive treatment. But after seven years of culling was complete, no evidence emerged of successful genetic change.
The average Boone & Crockett score of the standing crop of bucks in the moderate area was the same as it had been at the outset. That was also true in the control area. Despite one area being subjected to high-tech helicopter capture and culling for seven years, overall antler quality in that area remained the same as in the study area where zero bucks were culled.
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Why It Didn't Work
The Comanche Ranch study is the second major study of wild Texas deer to find that culling was ineffective. Dr. Mickey Hellickson's King Ranch study also found no change in antler quality after many years of intensive culling. But Comanche's more recent study had something the King Ranch study did not: DNA analysis.
Through DNA, Masa Ohnishi and Dr. Randy DeYoung were able to connect offspring to 963 buck fathers and build family trees of relationships for immediate relatives (fathers, sons and brothers). By studying these family connections in combination with the known antler measurements for each buck in the tree for some of them across multiple years the team established a "breeding value" for individual bucks: a buck's genetic value based on the antler quality of its offspring relative to the average for the population. A buck that produced offspring with above-average antlers for the population earned a higher breeding value, and vice versa.
If culling is to work, the criteria would need to remove bucks with lower breeding values while leaving bucks with higher breeding values to make more fawns. But the family trees revealed a brick wall: antler size was not correlated to breeding value. Therefore, you cannot predict the breeding value of a buck by looking at his antlers.
Over years of data, the research team found cull-worthy bucks with low-quality antlers that produced fawns that went on to have above-average antlers. They also found bucks with large antlers for their age that produced fawns with below-average antlers. Without being able to trust antler quality as a guide to a buck's breeding value, a hunter has no way to selectively cull.
https://www.qdma.com/qdm-works-culling-doesnt/?utm_source=newsletter&utm_medium=email&utm_campaign=2019-10-17&fbclid=IwAR3LODb32Jh91jlAM-Ezd9KDXG2G3MV1xsMcNNnvn1ZrHYMcK-BFcT21uDUQuote:
Focus on What Works
"I have no hesitation, no doubt, that culling in wild deer does not work," said Donnie. "Those who think they've had success aren't considering all the other factors involved."
Those factors include age, which is achieved by protecting most yearling bucks and increasing numbers of adults. They include nutrition, which is enhanced through habitat management techniques that increase forage production, like food plots, forest management, and prescribed fire, or though an intensive supplemental feeding program. They include techniques for encouraging mature bucks to use the land you hunt, like pressure management, sanctuaries, and cover production. Unlike culling, these techniques work.
Interesting article for sure, and it seems to be the first long term study on culling with the benefit of DNA testing. I'm one that has always logically believed and followed the idea of culling. To me the biggest surprise of this study was that bucks with the highest breeding value to produce large antlers often didn't have large antlers themselves.
