http://www.napa.ufl.edu/2000news/deer.htm
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 [Nov. 19] 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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