Wednesday, September 16, 2009

Researchers to evaluate additional deer population estimation methods

Researchers to evaluate additional deer population estimation methods
By Chris Jacques, DNR Research Scientist
Wisconsin DNR 2009 Fall Hunting Forecast

The Department of Natural Resources currently uses two main methods of estimating deer populations; the Sex- Age-Kill (SAK) model and an accounting-style model.

Mathematical models used to estimate game populations rely on certain assumptions. In the case of the department’s SAK population model, one of the key assumptions is that buck harvest rates are relatively stable over time. Because buck harvest rates are impacted by season structure – such as earn-a-buck, and hunter practices – such as Quality Deer Management (QDM), accounting style models are used in large areas of eastern and western farmland management regions.

Accounting style models are sensitive to and assume that the starting number or the “balance” in the checkbook analogy can be estimated with reasonable accuracy. Researchers at DNR’s Bureau of Science Services want to evaluate techniques to use in “calibrating” the accounting model to assure the greatest possible accuracy in that starting number over time. During the 2010-2012 timeframe researchers will evaluate the usefulness in Wisconsin of a method of aerial population sampling known as “aerial distance sampling.” They’ll do this using still other population estimating techniques for calibrating the important starting point for the accounting model of population estimation.

“It’s a little like sighting in a rifle,” says Jacques. “You bring home a new gun and sight it in at say, 200 yards. That first year it drives a tack at 200 and still kills deer for a couple more seasons. But then one day you sight on a deer’s vitals at 200, squeeze the trigger and in the scope see hair clipped at the top of the back…a pure miss. The gun’s accuracy has drifted over time.

The visual you witnessed in the scope was evidence of needing to resight or in the case of our model, using additional information or data to recalibrate deer population estimates for increased accuracy.”

For more information on this research effort contact Chris Jacques (608) 221-6358.

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