Wednesday, February 8th, 2023
Wednesday, February 8th, 2023

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Officials question DNR deer estimate

Editor

Madison Conservation Congress chairman Steve Oestreicher is
willing to accept the DNR’s revised 2002 deer population estimate
of 1.3 million, but he also hopes legislators will allow the
congress to spend $75,000 on an outside audit of the DNR’s
sex-age-kill (SAK) deer population formula.

Oestreicher is less willing to accept the DNR’s recommendation
for 49 Zone T units in 2003.

Last week, just days after the DNR announced its official
population estimate of 1.3 million deer heading into September of
2002, Oestreicher said he wanted university scientists from
Missouri, Colorado and Washington to conduct an audit on the DNR
SAK formula. It’s estimated that will cost $75,000, and Oestreicher
said he has already approached Rep. Russ Decker (D-Wausau) and Rep.
Scott Gunderson (R-Wind Lake) for the funding.

“Right now I’m looking for money for this audit,” Oestreicher
said. “There are people around the U.S. who have been studying SAK
and could come in here to conduct an audit.”

Oestreicher said he isn’t asking the DNR to abandon the SAK
formula in reaching deer population estimates, but he’s interested
in having the state learn whether there is a way to “tighten up”
those estimates.

He pointed to the discrepancy between last summer’s “herd
projection” and the current “population estimate.” Last summer, DNR
biologists projected that the state had 1.6 million deer heading
into the various fall deer seasons. Those projections are made
every spring, then are verified with the subsequent harvest
registration. Based on the 2002 bow, gun, muzzleloader, tribal and
CWD registrations, that original projection of 1.6 million was
“ground-checked” now at about 1.3 million heading into the fall of
2002.

“I’d like to get this audit completed as quickly as possible,”
Oestreicher said. “Somewhere in the neighborhood of half a million
deer have been lost by the SAK between last spring and now.”

One-half million? That might be a little high, according to DNR
wildlife officials.

DNR population ecologist Robert Rolley of Madison took a few
minutes to review the process the DNR uses to reach various
projections and estimates. Rolley explained that the DNR has to
make projections each spring for fall deer populations. Those
spring projections are then verified through hunter registration of
deer. The same process is being used right now to prepare for the
2003 deer seasons. Biologists will make projections in April and
May (they want to see how the winter finishes up) and will use
those projections to finalize antlerless quotas.

“The 1.6 million we thought we had last fall was a projection we
had (based on) last winter’s post-hunt estimate,” Rolley said.
“Every year we get a new harvest and then use that as the basis to
estimate the population that produced that harvest. From the 2002
harvest, we’ll calculate the actual estimate of the pre-hunt
population. From year to year, the population estimate could be
different than the projection heading in. A population projection’
is used to plan the harvest, then that projection is ground-proofed
by the harvest and deer registration.

“Based on that process, we’re now saying we went into fall with
about 1.3 million and came out with about 915,000 deer,” he said.
“We’ll make forecasts later in the winter about what we might
expect in the fall of 2003. By mid-March we finalize quota
plans.”

So, is the difference between the 2002 projection of 1.6 million
deer and the current estimate of 1.3 million (pre-hunt, 2002) a big
deal?

“Some people might want to make it a big deal,” Rolley said.
“There definitely were lots of things happening with this past
season that caused us to have a little less confidence in estimates
than a normal season.”

Some conservation groups that follow the annual herd population
estimates say the numerous Zone T seasons and resulting high
antlerless kills have made the SAK process less accurate, because
it relies heavily on the buck kill.

“That’s not a good generalization,” Rolley responds. “Some of
the areas where we had the most agreements between SAK and other
modeling was in the eastern farmland region where we’ve had Zone Ts
for several years now.”

Rolley said DNR biologists and wildlife managers had a number of
questions on how to interpret the harvest across the whole Northern
Forest Region.

“We saw a fairly substantial drop in buck kill in 2002 over what
we’d seen in 2001, both in archery and gun seasons. We tried to
interpret how much of that was due to reduced deer numbers, or for
other reasons, most of which surrounded the CWD issue.”

Right now, the DNR has the statewide over-winter deer population
at 915,000. The statewide over-winter goal is around 710,000 (now
that goals were lowered in CWD zones).

“We are looking at 45 to 50 Zone T units. That will be firmed up
and presented to the Natural Resources Board on Feb. 26. There will
be no earn-a-buck in 2003 Zone T units, outside the CWD zones, but
it could kick in in 2004,” Rolley said.

Conditions this winter are shaping up for another spring of good
fawn production.

“All indications are we should have good fawn production. We
could easily be back to 1.3 million by fall, but that’s not a
prediction,” Rolley said.

In the meantime, Oestreicher will begin contacting three outside
researchers on the possibility of conducting an SAK audit.

“The congress is still working with the DNR, but if there is a
way to improve our SAK formula, or the process we use in reaching
deer population estimates, why not do it?” he said. “The DNR is
being aggressive with antlerless quotas despite the fact that the
SAK came in lower than anticipated. I know they’re being aggressive
in the event there are more deer out there than the SAK is
showing.”

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