Fortunately, when the weather is harsh outside, I can come into a nice warm house, have a cup of hot coffee, and get cozy under a nice blanket, but what about the critters who live outside. How do they survive the cold? They must do okay, or you wouldn’t see all their tracks in the snow, and all of the babies born in the spring. I have woods that border my backyard, and I see many animals in my yard on a daily basis. I have so many deer, I can pick each one out when they are back there. I have one doe who has twins every year, and now her babies have twins. I never realized that deer had twins. How do these animals survive the weather? Although the cold presents challenges to the animals mother nature provides them with the tools to survive. All mammals must maintain a core temperature between ninety-seven and one hundred four degrees fahrenheit. Birds must maintain a slightly higher core temperature. If an animal’s core temperature drops below this range they will go into a state of torpor. In this state the body and the brain slow down similar to a vehicle going uphill with a heavy load, gradually slowing down more and more until they fall into a deep sleep from which they never wake up.
Energy conservation is the main thing that has to happen. While most of us ( humans ) try to lose a few pounds put on over the holidays and exercise more in January our animal friends are focused on holding onto their body fat and move around a lot less. There are a number of ways they accomplish this. Sleeping through the winter is one of the ways some members of the animal kingdom accomplish this. Some animals are true hibernators and accomplish this by letting their body temperatures and metabolism rate drop to levels well below normal to conserve energy. For example a groundhog’s body temperature drops from ninety-nine degrees to forty degrees, and their heart rate drops from 99 beats per minute to just 4 in hibernation, In this state an animal does not need to eat and can survive on the body fat they built up during the warm weather months. Contrary to popular belief black bears do not hibernate for the winter. They find a sheltered place and simply go to sleep there. They rely on their thick fur and stores of body fat to survive the winter. They will quickly awaken if disturbed, and can often be seen roaming around during warm, sunny breaks in the weather. In the winter squirrels spend most of the day and night sleeping in their nests. Their nests are well insulated and protect them from the winter wind, rain, and predators. Squirrels leave their nests for brief periods in the early morning and early evening to retrieve acorns and nuts they stored away in the fall. Research has shown that squirrels have excellent memories and can recall exactly where they buried their treasures. Because squirrels don’t expend much energy during most of the day, these stockpiles of food are enough to sustain them through the cold months. The absolute and undeniable master of winter woodland survival is the Whitetail Deer.
The state animal of Pennsylvania is perfectly adapted to the cold temperatures and deep snow we get each year. When we ( humans) go out in the winter we bundle up and put on layers of clothes quite different than the ones we would wear to a fourth of July picnic; instead of a short sleeve shirt or a light windbreaker we put on long sleeves and a heavy coat. Deer also put on a winter coat of sorts when the days start getting shorter. In summer a deer’s coat consists of a single layer of solid hairs. This thin coat doesn’t offer much insulation aiding the deer to keep cool when exerting itself in the summer heat. This coat doesn’t offer much protection against the cold. Instead when fall arrives the deer shed this coat and it is replaced by a much warmer one. The winter coat is made up of two layers, a thick furry undercoat protected by a layer of guard hairs. The winter guard hair is hollow. The hollow tube-like structure of the guard hairs traps air and heat. This protects the deer like a goose down coat. Deer are so well insulated that when snow lands on their back while they are sleeping, it doesn’t melt. The deer’s winter coat not only differs from the summer coat in structure, but also in color. In the summer a Whitetail deer’s coat is a reddish brown which serves to help them blend into the foliage of the woods. In the fall while shedding their summer coat the deer look kind of scruffy with tufts of loose hair hanging from their flanks. The warmer coat that replaces it is much darker, and ranges from gray brown to almost black in color. Deer were way ahead of us in the use of solar energy. Their dark winter coat absorbs more heat from the sun from the sun helping the deer to maintain their core temperature on sunny winter days.
During the fall, whitetail deer feed ravenously, packing on reserves of fat for the winter. Fortunately for them, the woods in which they live are full of nutritionally dense foods in the fall. In the woods acorns provide a high calorie food source, and farmers corn fields are irresistible to a hungry whitetail. They are always on the lookout for what I call deer lollipops. Deer lollipops are bird feeders. Deer will stand on their hind legs to fet the bird seed. They especially like black oil sunflower seeds. In fall, hormones trigger a weigh response. Which means that food consumed by deer during this period is automatically stored as fat on its body. Deer do not require as much food in the winter as they do in the summer. Their metabolism naturally slows down and in most cases they are less active. The exception to this are the bucks, who use up a large portion of their fat reserves chasing does during the mating season in January and February. “Browsing” is the main source of nutrition for whitetail deer in the winter months. Browse consists of the tender tips of buds of low hanging tree branches and shrubs. This not only helps them maintain their fat reserves, but also helps them maintain the chemical balance in their four chamber digestive system. Winter survival is a team effort for white tail deer. In the winter herds of white tail deer gather together in “ deer yards.” These areas provide ideal conditions for winter survival. They are close to feeding areas, and are sheltered from the wind. They are often located on a southern slope, where they can take advantage of warm sunny days. There are numerous advantages of forming a herd in the winter. Walking through snow uses a great deal of energy. It is much easier to follow a path in the snow made by the herd rather than trying to make their own paths. Like us, they prefer to travel on cleared plowed roads. In the summer, deer rarely move about in the daytime. The warmth of the winter sun causes them to be more active in the day time. That is why winter makes an excellent time to observe and photograph them. Deer also feel more comfortable in large herd which ads some protection from predators.