Snow on the ground gives hunters an advantage in spotting or tracking deer. / File/Gannett Wisconsin Media
Wisconsin officials annually set deer population goals based on input from the public, proposals from state wildlife managers and the Natural Resources Board, and then those figures are reviewed by the Legislature. Those population goals are designed to produce a balance of:
♦ A healthy herd
♦ A healthy ecosystem
♦ Few crop-damage complaints
♦ Sufficient hunting opportunities.
— Wisconsin DNR
Weather has been better for the deer than for the people who have hunted them over the past two years, according to two separate studies by the state Department of Natural Resources.
Outdoor conditions have a direct impact on the health of the deer herd, especially in Wisconsin’s northern region. However, they have only an indirect impact on hunter success because even ideal weather conditions for hunting can’t overcome other factors.
Hunters generally liked the weather in 2010 better than the year before. Archers also reported being generally more pleased with the weather last year in late September and early October than anyone during and after the gun deer season later in the year.
Opinions of the weather plummeted to near rock bottom in mid-December. Opinions remained consistently lukewarm throughout most of the 2009 seasons.
Brian Dhuey, the DNR’s wildlife survey and data base manager, began tallying hunter reactions to weather starting in 2009.
Information is gathered from deer stubs at deer registration stations.
“We asked about the number of deer seen, the hours hunted, the weather ranking on a scale of one to 10,” Dhuey said. “It’s conducted at the time of registration, so there’s no information about when hunters didn’t see deer.”
The study isn’t very scientific, because not all hunters like the same conditions, and those who bagged a deer are less likely to complain about the weather than a hunter who came home empty-handed. But it gives the DNR some ideas about whether the deer harvest was related to favorable conditions, said Bob Manwell, spokesman for the DNR’s land and wildlife management division.
The DNR also solicits hunter opinions online at its website. The advantage there is that unsuccessful hunters also have input, Dhuey said.
The weather report, rated on a scale of one to 10, is subjective, but “everyone probably agrees that a little bit of snow is good, so deer stand out against the rest of the brown out there, and also for tracking,” but few hunters like to deal with deep snow, Manwell said.
“And certainly cool is good, while severe cold is not,” he said.
Measuring the impact of weather conditions on deer is more scientific and has been going on much longer, although the study’s focus has been confined to Wisconsin’s northernmost region.
The DNR has been using its Winter Severity Index at about 35 locations in northern Wisconsin since the mid 1970s and used the index to measure back to 1960.
The index is calculated by adding the number of days with 18 inches or more of snow on the ground to the number of days when minimum temperatures were zero or below.
Under the system, a winter with a total of less than 50 is considered mild, 50 to 80 is moderate, and above 80 is severe. Totals above 100 are considered very severe.
When the index numbers are high in northern Wisconsin, deer survival over winter is lower, fewer fawns survive and adult buck harvests fall.
In all but the northernmost counties, winter generally isn’t severe enough to affect the deer population, Manwell said.
In the north, weather has generally been favorable for deer survival and reproduction for the last 13 years, according to the DNR study.
It scored in the “mild” range in all but four years in that period. It reached “moderate” levels — a score of between 50 and 80 for the season — three times and strayed above 80, a “severe” level, once in the period.
The index strayed into the “very severe” category — over 100 — eight times since the winter of 1960-61, with the worst being the winter of 1995-96, at 127. That year and the following year, which also was “very severe,” accounted for a 35 percent decrease in the deer population in the north, according to the DNR.
Conversely, a stretch of mild winters in the 1980s resulted in spectacular increases in deer population, according to the DNR.
Contact Paul Srubas at firstname.lastname@example.org.