GAINESVILLE, Fla. --- As fall hunting season opens in Florida and other states, a University of Florida professor says America's native white-tailed deer have some unique ways to compensate for hunting.
Hunters most often pursue bucks, both for trophy value and because shooting does in many states is illegal or highly restricted. That might seem to threaten deer populations because it cuts into the number of males available to mate. But Ron Labisky, a UF professor of wildlife ecology and conservation, says his research shows that deer make up for the loss of bucks with a unique response: Does in areas where hunting is allowed give birth to considerably more male fawns than female fawns.
"We don't usually give animals due credit for their persistence, especially deer," said Labisky, who has spent three decades researching white-tailed deer. "With males-only hunting, it is very, very difficult to deplete a deer population."
General deer hunting season opens at different times in Florida during the fall (the season opens this Sunday in Central Florida). While it typically lasts through January or February, hunters are allowed only two days to kill deer that have no antlers, including does.
Labisky and colleagues examined the reproductive tracts of 380 legally harvested does from four areas of Florida. The Tosohatchee State Preserve and most of Eglin Air Force Base are off limits to hunting, whereas it is allowed in Camp Blanding Wildlife Management Area and the Rotenberger Wildlife Management Area.
More than 90 percent of the does in all the areas were pregnant, the research found. Males comprised 56 percent of the fetuses in the hunted areas but just 39 percent in the non-hunted areas, it found. As if that weren't enough, the researchers also found 38 percent of does on hunted sites carried twins, compared with just 14 percent on non-hunted sites.
"Productivity was higher on hunted than non-hunted sites," wrote Labisky in a summary of the study, which appeared in the Journal of Wildlife Management.
Why would deer give birth to more males in areas where bucks are hunted? Labisky said the doe's reproductive cycle offers one explanation for the adaptation.
Does typically go into heat for about 72 hours, he said. In non-hunted areas, they find mates quickly, while they take longer to find mates in hunted areas. The later does breed while they're in heat, the greater the proportion of male fetuses, Labisky said.
In a related research project, Labisky found that while does typically wait for bucks to find them, they actually seek out bucks in hunted areas where there are fewer around.
From the white-tailed deers' perspective, the findings are good news. On the other hand, the research likely means the animals will continue to be a nuisance in some states.
Labisky said experts believe the population of deer in the United States is about equal to what it was before Europeans arrived, with somewhere between 24 million and 34 million nationwide. That's up from just 350,000 in 1900, when the population crashed largely because of unregulated hunting.
Northern states have the biggest problem with overpopulation of deer because their fields provide so much forage -- at a time when many of the deer's traditional predators such as wolves and bears no longer pose a threat. Deer in the Midwest also give birth to more fawns, and more of the fawns survive, than in the South, Labisky's research has found.
In Florida, by contrast, "our groceries aren't as good," Labisky said. Unlike states such as Wisconsin, with at least 2 million deer, Florida has about 600,000 deer.
The state's deer population is relatively stable -- in part because of the deer's unique compensation to hunting, Labisky said.
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