The first time I heard that saying was when I was a little kid, it was 15 below, the wind howling, snow blowing and I was freezing. I wondered how the animals, insects, and plants were able to survive these harsh conditions. I was able to bundle up in layers, go inside and sit by the fireplace, or get into my bed and get under the down comforter to get warm. That begs the question, how do our native species stay warm and survive in such brutal conditions as we have been experiencing lately?
There are two main issues facing anything living outside during harsh conditions, where to find food and dealing with cold temperatures. Snow is not a significant issue, in fact some species need it to survive the harsh conditions. Mice and voles live in the “subnivean” zone. The area between the snow pack and ground. The snow acts as an insulator from the cold temperatures and it also provides protection from predators.
In order to sustain life, you need an energy source (food) to power bodily functions. Fruits, seeds, other animals, fat reserves, twigs, and nuts are just some of the energy sources many species are looking for to carry them through harsh times. Conventional wisdom says that managing energy resources then, is the biggest key to survival. So how do they do it? Their survival is predicated on specialized adaptations to winter that have evolved over time. Simply put, migration, some form of dormancy, and being a tough guy are the three main strategies that all species use in one form or another. Chemical and physical changes also play a major role in several species survival.
Migration is a term with which we are all familiar. However, migration means different things to different species. We all know most of our birds migrate south for the winter to the balmy coasts of Florida and South America. But “south” is a relative term. The Rough Legged Hawks, American Tree sparrows, Dark Eyed Juncos, Snow Buntings and a few other species consider Ohio “south”. Their breeding grounds are far north in Canada and the Arctic circle. Biologists use the term “migration” for other species as well and have been able to track some of these migration patterns. Reptiles and amphibians “migrate” to protected places underground or underwater to avoid freezing temperatures. Fish will “migrate” to different layers of waters within a lake or pond. Dog ticks migrate or burrow in the ground once temperatures get cold enough and emerge once the ground warms up. Plus,we all have experienced the “migration” of the Asian ladybird beetle and Cluster flies into the nooks and crannies of our houses, not to mention field mice, in the fall.
The second strategy, dormancy, has several meanings as well. Many of our non-migratory birds enter a state of dormancy each night in order to conserve energy. This is state of dormancy is called torpor. Torpor is a controlled reduction in an animals metabolism, low oxygen consumption and lower body temperatures are indicative of this condition. A key part of the definition is “accurate metabolic control.” It is a phenomenon restricted to warm-blooded animals. Animals enter “daily”, “periodic” or “seasonal” torpor depending on environmental conditions. Seasonal torpor or “hibernation” is what we commonly think of when we think about animals sleeping through the winter. Chipmunks, certain mice, bats and groundhogs are examples of true hibernators. True hibernators cannot be easily “woken up”, unless your name is Puxatawney Phil and he needs to look for his shadow. Contrary to popular belief, bears are not true hibernators.
Cold-blooded animals handle dormancy in a different way. Their reduced state of metabolic activity is largely controlled by environmental conditions. Reptiles and amphibians must become dormant during the winter because they lack the “internal control “over their metabolism.
Many of these species seek sheltered places and undergo chemical changes to prevent their tissues from freezing. Chemicals associated with this type of dormancy are various sugars and certain alcohols such as glycerol and ethylene glycol. Some frogs can tolerate certain levels of ice between cells and can actually freeze solid. Spring peepers, chorus frogs, gray tree frogs, and wood frogs tolerate and regulate a frozen state which allows them to “awaken” in March to begin their melodious chorus. As was mentioned earlier, good snow cover is essential to their survival as they overwinter under leaf litter on the forest floor. Some snake species congregate in groups during the harsh weather as a way to conserve heat energy. Then they go their separate ways once it warms up. Insects overwinter as eggs, pupae, or adults. The Morning Cloak and the Angle Wing butterflies overwinter as adults and are the first to be seen on warm spring days. Chemical changes occur within their bodies to protect them from dying during the harsh winter conditions.
The last strategy is to “be a tough guy”. In order to survive, these species must consume enough food to survive the harsh winter conditions. Coopers hawks feed on birds that are eating seeds at the bird feeder. Foxes feed on mice and voles. Rabbits feed on tree bark and twigs. Unfortunately, some are not as tough as others and don’t make it through harsh times. Overall larger body size, smaller ears, and circulatory systems that can conserve heat are some of the traits that have evolved in our native species which allows them to survive in harsh climates. One of the primary ways these species tough it out is to add layers of fat to their body. This fat is somewhat different than the fat we are accustomed to, it is called “brown fat.” Brown fat’s main function is to generate body heat. Animals produce brown fat as they gorge themselves just prior to the onset of winter. An ample layer of fat is all they need along with another adaptation… fur. Fur consists of two layers, the ground hair and guard hair. The principal function of ground hair is to maintain the animal’s body temperature and that the guard hair is to protect the underlying fur and skin and to shed rain or snow. Some species add an additional layer of ground hair, while some increase the guard hair length, and others do both.
So next time it is -15 and you are feeling sorry for the animals outside, don’t worry, they are just fine. For them it is fit outside! Stay warm…spring is on its way, I promise.