By Staff
Can you believe this weather? I can't remember when it has stayed this cold and snowy this early for so long. Thinking back, it's not unusual to get tracking snow and even sub zero temperatures during the November deer season but it only lasted a week or two at most.
Then it would warm back up and we'd sit around all through December wondering if we'd have snow for Christmas. As I recall this snow came about the opening of deer season, Nov. 15 and has been around ever since. According to the forecast it has no intention of leaving anytime soon, either. Do you suppose global warming is on vacation?
Anytime we get unusually cold weather early in the season I start to wonder how the deer are going to make out. If they have to start tapping their fat reserves too early it can mean trouble. Most of the time my concerns are unfounded. Deer have evolved to survive cold northern winters by developing some marvelous traits that help them cope with the cold, deep snow and limited amounts of poor quality food.
In the fall they don their winter suits, dense, wooly under fur covered by long, hollow guard hairs which together provide the ultimate insulation and water proofing. At the same time they start accumulating heavy fat reserves. These adaptations are hormonally driven triggered by a decrease in daylight. It happens regardless of what the weather is or isn't doing. The prospect of a deer surviving winter depends on the amount of fat stored and the rate at which it is used up. Even undernourished deer forego body growth to store what fat they can. Here in the northern part of whitetail range it's inevitable that deer are going to lose weight over the winter. If its fat tank is full going into the winter a deer can survive up to 30 percent weight loss.
Another survival technique northern deer have is to migrate to wintering areas different from their fall, fat building range. These are often called yards but only in certain areas of their northernmost range do they truly gather in defined yards. More often it would be better described as a loose congregation of animals. This ensures a plentiful supply of unused browse. This shift can be just a few miles or 50 miles or more with the average being about eight miles. These winter areas must provide shelter from snow and wind. For this deer prefer dense stands of evergreens, especially cedar. Surprisingly, cedar is the only natural food source that can single handedly provide enough nutrition to carry deer through the winter. Everything else requires other back-up forage. Spruce stands are their second choice. The various pines and hemlock are not palatable so come in a very distant third. Evergreen stands are scarce here in southern Michigan so deer typically go to brushy river bottoms. Does live in maternal family groups comprised of mothers, fawns, aunts and grandmothers. Bucks live in unrelated bachelor groups. It's stressful for various groups to commingle in the winter area but it has its advantages in predator detection and keeping snow packed down for mobility.
As winter sets in and the deer get snuggled into their wintering ground physiological changes occur. To save energy their metabolism and thyroid function drops and they reduce mobility. By midwinter they are in an almost semi-hibernation state. Regardless how much food is available their food intake has dropped 30 percent and their movement decreased by 50 percent. These energy saving tactics also help them endure the crowded, hostile conditions. Normally this gets most of them through. However, if early cold conditions persist and coincide with a late winter breakup the result can be disastrous. This happened in the winter of 1996-97 throughout much of their northern range and hundreds of thousands died. However, nature has even this planned out. Fawns have the least amount of fat and are the first to go. They are expendable. Bucks are next because they were off doing guy things (fighting and breeding) in the fall instead of building fat. That saves what food is left for the mothers of procreation, the adult does. Ain't nature somethin'? Carpe diem.