Not all early winters are disastrous for whitetails, but the 1991 Halloween snowstorm that swept northern Wisconsin set the state for one of those severe winters that produced unpredictable consequences.
The storm blanketed the region with nearly 30 inches of snow three weeks before the state’s traditional rifle deer season opened. Another 18 inches fell during the first weekend of the season.
According to Wisconsin DNR Wildlife Biologist Keith McCaffery, many bucks were in such poor physical condition they cast their antlers by the end of November. Others reportedly came off while bucks were being dragged out of the woods by hunters.
Given what we know about white-tailed deer reproductive physiology, it’s likely the rut was essentially over by the end of November across northern parts of the state. As a result, 20 percent or more of the adult does probably failed to breed.
In addition, subsequent newborn fawn mortality must have been greater than 50 percent, as evidenced by state deer harvest results the next two years.
The Wisconsin DNR predicted a 1992 rifle season kill of between 330,000 and 370,000 deer. Although respectable, the actual kill dropped to 288,906 deer — 12 to 21 percent lower than expected. The resultant low fawn recruitment in 1992 impacted the 1993 deer kill even more, when hunters took only 217,584 deer. Some winter deer-kill is expected across Northern deer range every winter. Usually, fawns comprise 80 to 90 percent of the malnutrition- related loss. However, during prolonged winters adult deer make up about 50 percent of the loss, and 50 to 70 percent of the newborn fawns might die the following spring.
For those who doubt the potential impact of early winter onset, I suggest they harken back to the effects of northern Wisconsin’s 1991 Halloween snowstorm — and to the failure of professionals to predict the outcome.
Just remember, deer population models are only as good as the data that go into them. Sometimes there is no substitute for putting on a pair of snowshoes and getting out into the whitetail’s real world to more accurately determine those numbers.
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