Taking advantage of fresh snow and some vacation time over the holidays, two other hunters and I were geared up for doe and posted halfway down a steep ravine in Allegheny County. Across the tight valley, conducting more of an abrupt flush than a drive, the leader of our party rushed into a dense patch of conifers behind a suburban home.
Five deer busted out of the cover and bolted into the ravine -- every one a buck ranging in size from a half rack to a bulky mature eight-point.
That's not something we would have seen a month earlier.
White-tailed deer clustered in bachelor groups tend to break up in late summer, nudged into competition by the first hormonal rumblings of the rut. Driven by glands and instincts, the bucks' typically cautious behaviors are replaced by an overwhelming urge to mate. Doe activity also changes during the rut, which in Pennsylvania starts to recede by the opening day of the statewide rifle deer season.
After the rut, it's a whole new hunt.
"The bucks, if they're smart, focus on conserving energy," said Duane Diefenbach, an adjunct professor of wildlife ecology at Penn State and leader of the Pennsylvania Cooperative Fish and Wildlife Research Unit. "During the breeding season, bucks don't store fat, so in winter -- particularly when there's snow and food is harder to find -- their metabolism is down and they're essentially in survival mode."
Does, which spent the autumn eating and building a layer of fat while attracting mates, are less susceptible to the challenges of winter. But they, too, experience a drop in metabolism and are physiologically changed after the rut.
"Mature does, almost all of them, are pregnant by now," Diefenbach said. "If a doe doesn't get bred, she will cycle again and attempt to attract a mate. She'll start to feed more in about March, when her metabolism ramps up and she's not only sustaining herself but producing an embryo."
In the winter, male deer lose their most distinguishing feature. Antlers serve as a mechanism for competing for mates. During the post-rut, when antlers are no longer necessary, testosterone levels drop, causing the loss of a layer of cells at the base of the antlers.
"I'm not sure if anyone really understands the process, but the length of daylight and weather and food conditions influence the physiology of these male deer and causes variations that lead to their dropping their antlers," Diefenbach said. "As those cells are depleted, it dissolves the bond linking the antler to the skull, and the antler is shed. It could happen any time after the peak of the rut. Some keep their antlers longer."
Understanding post-rut behaviors can inform late-season hunters as they adjust their tactics. While Pennsylvania winters aren't as severe as those farther north, deer in January are focused on conserving energy. They're less mobile and more likely to rest near warmer spots close to easily accessible food sources.
"You'll see beds under hemlocks. They're more inclined to be on south-facing slopes where the sun is coming in and the snow isn't as deep," Diefenbach said. "In forested areas, they're looking for browse and regenerating clear-cuts. In mixed forestland, they're going out at night in corn and soy fields looking for waste grain and browsing in the forest."
Pennsylvania deer are experiencing a long-term change that probably improves winter mortality rates and certainly impacts hunters. Before the implementation of controversial antler restrictions, imposed in the last decade to reverse negative changes in the deer's sex ratio, about 80 percent of antlered deer were 1 1/2 years old, according to Game Commission estimates. Now PGC data shows about 40 percent of antlered deer are 2 1/2 years old.
"Because of the changes in hunting regulations, the male side of the population is much older now," said Diefenbach, who was among the PGC-led group of deer specialists that devised the antler restrictions. "It varies by management unit, but we've more than doubled the number of 2 1/2 year and older bucks in the state."
Ample deer-hunting opportunities remain. Statewide, archery and flintlock equipment (but not in-line muzzleloaders) may be used for antlered and antlerless deer through Saturday. In three management units, including 2B, which covers most of Allegheny County, bucks and does can be legally taken with archery and flintlock gear through Jan. 26. Also in 2B, where some 6,000 doe tags remain available, antlerless deer can be hunted with rifles (slug guns in Allegheny County) through Jan. 26.