Boom or Bust

Weather has an effect on big game. In the short term, whitetails might bed on the lee side of a hill during a snowstorm, then rush to resume feeding soon after the storm abates. Or on windy evenings they may elect to feed all night in the woods rather than expose themselves to severe wind chill in an open agricultural lot. But weather can also have long-term consequences. It can selectively increase or decrease the number of animals over a period of time. These population changes can have a reverberating effect for several seasons to come. Let me explain.

One year I was still-hunting through a block of hardwoods in Upstate New York when I came upon a grove of giant oaks that had been devoid of acorns for several seasons. The weather the previous spring and summer had apparently been quite favorable, however, and the ground was covered with the oblong nuts--so many, in fact, it was like walking on ball bearings.

This stand of oaks had not drawn whitetails for years, but without warning there was sign everywhere, indicating that the deer had returned, drawn from points unknown to feed on the bumper crop. I returned the next evening and still-hunted along a fresh scrape line, where I tagged a fat 7-pointer within hours of entering the woods. When I finished field dressing the buck, I opened his stomach and found he had been gorging on green-and-brown acorns for several days.

What's all this have to do with long-term deer population numbers? Biologists tell us that when the mast crop is heavy, Northern whitetails will enter the hard months of winter with plenty of fat reserves. Bucks, fawns, yearlings and does all benefit from this bounty, allowing more of them to survive until the following spring.

If you're a buck hunter, however, a poor mast crop can have a far-reaching and deleterious effect. In some areas trophy bucks will be the first to die off during a hard winter. This is due in part to the rigors of the rut, which can cause them to loose 25 percent or more of their body weight before the snow flies. Other bucks will suffer too, especially button bucks, leaving fewer bucks of each age class alive by winter's end. Thus, a poor mast crop, caused in part by adverse weather conditions such as a late spring frost or a summer drought, coupled with deep snow and prolonged cold temperatures, can be the kiss of death, resulting in fewer mature bucks during the following four or five years.

Winter storms and mast production are not the only weather conditions that affect deer. According to Jerry Cooke, Texas game-ranch chief, water, and not acorn production, can be the dominant factor, especially when it comes to Texas deer management.

"Too much water or a lack of water can have long-term negative effects on deer populations," says Cooke. "In either case, timing is important. For example, if you have a dry fall or a dry winter here in Texas, it will have a negative effect on antler growth the following season. In some cases this may result in fat deer with small racks or skinny deer with huge racks.

"Besides timing, location can also be a factor. A dry spring or early summer in West Texas, for example, can affect fawn survival. A lack of nutritious forbs reduces a doe's milk production. No milk, no fawns," Cooke says. "A lot of rain in East Texas, however, can flood rivers causing an outbreak of salmonella, a naturally occurring bacterium in these riverbottoms. Once afflicted, fawns die of dehydration rather quickly.