Unusually high deer birth rate spurs debate on lethal culling
- By: David Campbell , Staff Writer
Many explanations for large number of fawns among deer receiving
Opponents of lethal deer management have been saying for years that
killing deer is futile because it only spurs reproduction.
And a recent disclosure of an unexpectedly high fertility rate among
immunized deer by the Yale-educated wildlife biologist overseeing
Princeton Township's experimental deer birth-control program only
confirms that claim, they say.
Last week, White Buffalo President Anthony DeNicola met with the
Township Committee seeking about $27,000 to conduct the majority of
third-round deer immunizations in August. The money would have been
requested anyway to do the vaccinations this coming winter, when they
were originally planned, he said.
Seventy-eight does have been treated with experimental one-shot
vaccine SpayVac in the study area in the southeastern corner of the
township. Seven of those deer have died for reasons unrelated to the
vaccinations. The experimental program began in the winter of 2003.
Mr. DeNicola has said an unexpectedly high number of fawns became
pregnant prior to last winter's round of treatments in the study area -
the birth rate is about twice that of deer in areas where population has
been managed through lethal sharpshooting and captive bolting. If the
trend continues, the wildlife biologist said, births will outweigh
natural deaths in the study area, and the township will not see the
desired population reduction.
The cause of the apparent reproductive anomaly is unclear, Mr.
DeNicola said. It may be that the study area is in a heavily landscaped
area with an abundance of foraging opportunities not available in parts
of the township where culling has occurred, which he described as
naturally wooded and already heavily browsed by deer.
Another possibility may be that the founding population of does that
first settled in the study area - a densely housed corner of the
township that is not especially attractive to deer, he said - were
genetically predisposed to high rates of fertility.
"Why the research area has this unusual level of reproduction at this
point I cannot explain," Mr. DeNicola said. But he said this
reproductive "fluke" can hardly be held up as proof that culling in the
other parts of the township has spurred a wave of reproduction and
thereby has backfired.
If that were the case, he said, the township would be seeing a
comparable jump in the birth rate among deer in other parts of the
township where culling has occurred, which he said it hasn't.
But Nancy Bowman of the Mercer County Deer Alliance, a longtime
opponent of the township's deer cull, says otherwise. She said the
reproductive spike in the study area proves what she and fellow
animal-protection activists have been saying for years.
"When a significant number of deer are killed and the food supply and
other factors remain about the same, it doesn't take a Yale-trained
anything to figure out there should be more fawn survival, more does
pregnant, and does mating younger than before," she said.
Since the higher fertility rate is in the township's birth-control
area where culling hasn't occurred, Ms. Bowman reasoned, the township is
most likely witnessing "refuge seeking" by deer fleeing the cull areas.
She said: "Deer have moved from where DeNicola is killing to where he
is not killing - a predictable result."
Mr. DeNicola conceded that the birth rate in culling areas has
increased - maybe 10 percent, he said - but he described the rise as
"minimal." He said deer were already reproducing at a high rate of about
80 percent of their "maximal reproductive potential" in cull areas when
the program began in 2001.
"You couldn't get them to go much higher," he said. The wildlife
specialist said deer in cull areas are now reproducing even closer to
the maximum than when culling began, but added that, taking into account
the fact that the population has been reduced by about 70 percent, a
10-percent rise in fertility to date is relatively minimal.
As for "refuge seeking," Mr. DeNicola said his study team has not
witnessed any influx of deer into the study area.
But Sue Russell, policy director with Rumson-based Center for Animal
Protection, said the claim by Mr. DeNicola about reproduction rates
already being high is one she's heard before, and she said it misses the
"We say an increase will happen, they always come back and say it's
incremental," Ms. Russell said. "If their rate is already high and you
do something extra to kill them, it'll go a little higher, but not much
"But people miss the point," she continued. "You're keeping the rate
high, and that seems always to get lost. You're keeping them in the
rapid-growth phase of their cycle."
Ms. Russell said she wasn't sure if the high fertility rate in the
study area is a "fluke" as Mr. DeNicola said. "If they were already
pregnant with high numbers, it's a symptom of how wrongly they have been
managing deer," she said. "If you are removing hundreds of deer, the
survivors are going to breed like crazy. Those that have less stress are
going to breed earlier."
Ms. Russell said she believes the current township administration
will not change its policies and will have to keep killing deer, adding:
"Give that five years, and you will have a total deer farm in Princeton.
It's going to be like rabbits."
Jay Kirkpatrick of ZooMontana, one of the two suppliers worldwide of
the contraceptive ingredient in SpayVac, said an outside objective and
systematic population study would be needed to isolate the cause of the
spike in fertility in the study area.
Mr. Kirkpatrick said he's no deer biologist, but that when increases
like that are witnessed in wild animal populations, "You can generally
start looking at weather, grass, food, habitat, things of that nature."
But he concurred that population reduction speeds reproduction rates
- "that's zoology 101 in your freshman year in college. We refer to it
as density-dependent reproduction. In virtually every species from rats
to you name it, if you reduce populations, they simply speed up their
Mr. Kirkpatrick added that when it comes to deer population control,
he steers well clear. He said he wants nothing to do with it, and that's
because of the political turmoil that comes with it.
"We don't touch deer contraception because of the irrational
arguments that swirl about it," he said. "Objectivity vanished long ago.
We just backed away."
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