Do Top Bucks Dominate Deer Breeding?

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Wisconsin trophy buck
A Wisconsin trophy buck shot on this family’s farm in southwestern Wisconsin. Deer hunters often presume prime bucks do most of the breeding, but some do no breeding at all.

Bracing his feet in the snow-covered leaves, a deer hunter reached down and helped his young daughter over a log on the steep hillside in southwestern Wisconsin. It was the second morning of deer season, and they were making a long, slow deer drive in hopes of pushing deer past his uncle and cousins.

Just as the two resumed their walk, they heard a single shot from his uncle’s .30-06 across the wooded valley. More than 45 minutes passed by the time they completed their loop and reached his tree stand. They found a gut pile near the tree stand, and then followed drag furrows all the way to the road. They wondered aloud why his uncle had been in such a rush to drag the deer that far by himself. As they neared the road, they saw him standing over a buck, a long main beam sticking far above the snow-glazed grass.

They had never seen his uncle so excited about a deer, and with good reason. This 3½ -year-old buck carried a wide 8-point rack and, nearly 20 years later, it remains the second-largest buck anyone has killed on this farm. After he told us his story about shooting the buck at 15 yards as it followed a doe under his tree stand, he almost apologized for shooting it.

“I kind of hated to take him out of the herd before he had a chance to breed her,” he said. “It would have been nice to let him pass his genes along.”

The deer hunter assured his uncle the buck had probably already done the bulk of his breeding. It was Nov. 24, after all, and breeding activity was on the slide.

Faulty Assumptions?

But what if that buck had been trying to breed that doe? And if it bred several does before stopping his uncle’s bullet, had it gotten any of them pregnant? Deer hunters often assume every buck is trying to breed, and that the biggest bucks do the most breeding. In fact, in some areas where hunting pressure is controlled, deer hunters even pass up certain monster bucks in hopes they’ll pass their antler traits to their offspring.

Are such assumptions and deer management practices accurate and worthwhile? Research suggests older bucks do indeed breed more successfully than yearling bucks, but that doesn’t mean mature bucks always succeed and yearlings always fail. Far less certain is whether the most impressive bucks often breed successfully. Based on the available genetic studies and field observations from researchers, it’s more likely an older buck with average antlers produces more fawns than the cover-photo buck with the monstrous rack.

Valerius Geist, professor emeritus at the University of Calgary in Alberta, says there’s a simple reason for that: Where natural selection is concerned, average is king. That rule also applies to humans. Look around. What’s more common in our world, couples who look like Brad Pitt and Angela Jolie or Fred and Ethel Mertz?

Geist also cites computer studies of women’s faces. “When the faces of cute girls are averaged by computer, the prettiest face is the most average one!” he said. “So, run-of-the-mill bucks are there because average is most common, and average propagates more than the trophy variety.”

monster buck
There’s far more average bucks on the landscape than monster bucks. The rule “average is king” applies to deer and humans. What’s more common, couples who look like Brad Pitt and Angelina Jolie or Fred and Ethel Mertz from “I Love Lucy”?

Oklahoma Research

From 1992 through about 2001, researchers from Mississippi State University studied an Oklahoma deer herd to learn which bucks did the breeding. Among their findings is that if deer hunters are practicing selective harvest in hopes of improving a herd’s genetics, the focus better be intense because breeding success is extremely unpredictable. And if hunters are hoping buck with the largest, most handsome rack will pass its genes onto every available doe it encounters, they’ll probably be disappointed.

As researcher Randy W. DeYoung said at the 2002 Southeast Deer Study Group meeting in Mobile, Ala., the most successful breeders are usually nothing special to look at. DeYoung and his fellow researchers studied a whitetail herd on a 3,000-acre property in south-central Oklahoma. The property is surrounded by a fence, which Young described as “a strong suggestion rather than an actual barrier.” Deer from the property were often seen or harvested on neighboring lands.

The age structure of the herd’s bucks was slanted toward younger deer, with yearlings making up about 44 percent of the males. Further, bucks 3½ years or older made up 30 percent of the males. During the studies, the herd’s buck-to-doe ratios ranged from 1-1 to 1-2.5.

Researchers collected samples of blood, muscle tissue or antler tissue to obtain DNA markers on deer so they could trace their lineage. The samples came from shed antlers, deer shot by hunters, and deer captured with drop nets. Tags on living deer, antler identifications, and photos and video clips allowed researchers to identify and age individual bucks. By cataloging the DNA samples and comparing them with new samples each year, researchers identified which bucks did the breeding each autumn.

From 1992 to 2001, the team sampled 441 different deer, of which they knew the exact age of 265. They charted the DNA for about 145 of these deer, which included 53 bucks. Of those DNA-identified bucks, researchers knew the exact age of 35 individuals. Those 35 bucks had sired 91 fawns through 2001.

Who’s Breeding?

So, which bucks did the breeding? DeYoung reported reproductive success was highest for older bucks. About 65 percent of siring in the Oklahoma herd was done by bucks at least 3½ years old, even though they comprised only 30 percent of the buck population. Yearling bucks sired only 12 percent of the fawns, even though they comprised 44 percent of the bucks.

By studying the data further, researchers concluded most bucks were at least 2½ years old before they started breeding. A few bucks, however, didn’t start breeding until later.

“By far, the bucks’ median age for reproduction was 2½ years,” DeYoung said.

What percentage of buckssucceeded in their reproduction efforts? By comparing successful breeding bucks with the total number of bucks that were likely to be sires, researchers determined only 20 percent of all bucks were breeding in any given year. Further, even if they were successful breeders, most bucks didn’t produce more than one fawn in their lifetime. Although some bucks produced multiple fawns during their lives, the average remained one for a lifetime of breeding.

Which bucks produced more than one fawn? DeYoung said a buck, whose ID number was 141, sired 13 fawns between 1994 and 2000. “This guy wasn’t much to look at for antlers, but he must have been a heck of a dancer,” DeYoung said. “He was the ultimate plugger. He never sired many fawns in a single year, but he was consistently successful.”

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