Originally published in 2010, I thought this post was fitting for the present season. Enjoy!
Gone are green leaves on deciduous northern hardwood trees. Now in dormancy the trees no longer need sustenance from sun light. Withering or marcescent leaves hang on to branchlets providing harbor from cold northwest winds for next year’s buds and birds that take advantage of this cover during the colder months. Oaks and the American beech are known for leaves that hang on well into the winter. These marcescent leaves stay put because they don’t form an abscission layer which is necessary for the leave to fall away from the tree. These trees produce the hormone auxin that prevents the formation of ethylene, the chemical that causes abscission.
It is near last call for painted turtles to make use of basking habitat, a wonderful way to loosen the joints and recharge the body for this ectothermic animal as it takes advantage of the sun on a cool day. Soon the liquid molecules on these northern ponds will slow so much that they turn from water to ice, inhibiting the turtle’s use of basking habitat. Painted turtles brumate meaning their metabolism slows down to a point where it requires few outside resources to survive the long winter. The turtles bury themselves in pond bottom detritus in an environment below the depths of frozen water and utilize cells in their tail to occasionally introduce oxygen into their bodies throughout the long, frozen winter.
Changed are terrestrial environs. Once soft and supple earth hardens with frost and becomes nearly impenetrable. Wood frogs who like to take advantage of vernal pools in the very earliest spring cannot afford to be frozen into an earthen vault and so have adapted to surviving winters hidden beneath a layer of dropped leaves. One would think that these adaptive amphibians would freeze solid so close to the surface in below zero temperatures but in fact these frogsicles have evolved to having internal systems that prevent their cells from freezing to the core. These curious creatures have nucleators that allow them to freeze at a temperature very close to zero degrees Celsius and this actually slows the formation of ice and allows timely metabolic reactions. Second they turn sugar into alcohol that keeps critical cells from freezing. The alcohol within the cells allows ice to form on the outside of organs by sucking water to the outside of the organ and leaving a thick gooey antifreeze behind. Thirdly wood frogs have a very slow metabolic rate utilizing very little oxygen allowing dormancy to last appropriate lengths for cold climates. In the early spring when the sun is reaching higher levels in the skies the wood frogs are amongst the first cold blooded animals to unfreeze with the surface of the earth. This allows them to access breeding habitat early in the season which may be a secret to their survival success.
Conifers dominate the winter country. These adaptive trees are uniquely qualified to survive the harsh conditions of the north when the sun is low. Conifers retain their dark green needles. This enables the tree to act as a solar energy collector and stay relatively warm, allowing minimum metabolism to continue even in the harshest conditions. The needles are often coated with a waxy substance and shaped to shed snow. The narrow needles prevent water loss during the winter months due to their small surface area. These trees are often shaped like an arrow pointing up into the sky which keeps the heavy snow from accumulating and breaking branches. Most conifers have branches that are remarkably flexible as compared to hardwood trees. This trait keeps the tree from being injured during the winter, a time when an injury can mean death to the tree.
Goundhogs slip away into deep burrows below the frost line. There the fall into profound hibernation for the duration of the winter. During hibernation their body temperatures falls to levels that are a few degrees above the freezing mark, their metabolism slows down to almost a standstill, and breathing and heart beats happen only a few times each minute. Chipmunks also live in burrows during the winter but do not hibernate. They store lots of extra food like acorns, dried berries, nuts, and seeds in extra chambers within their burrows and consume them slowly throughout the winter. They do sleep throughout much of the winter but may appear above the surface on warmer days and when food supplies run low.
And when the seasons change so do some mammals. Snowshoe hares shed their summer coat which is brown like the forest floor and adopt a perfect camouflage for winter conditions as their thick fur turns white. Large feet covered with massive amounts of hair help to keep this rabbit on top of deep snows allowing it to conserve energy. The trick to varying hare winter survival is to find a good foraging area before the snow flies so that this furry animal does not have to utilize energy in search of food. Hares that survive usually find good habitat that is near cover that lessens snow depth and has ample food for the winter. Of course there are predators that may choose to take advantage of that.
In the kingdom of insects ants let winter slip away by becoming a lean and mean colony. Queens and selected workers live off of stored food supplies by reducing the colony numbers in autumn before the depths of winter settle in. All of the males are given the boot and perish as they freeze outside of the colony at the outset of the winter months. New males, necessary only for breeding, will be reared in the warmer weather when the queen needs a mate to produce new members of the colony.
Winter means isolation for many animal species and none are more isolated than the queen bumble bee. These social insects abandon the subterranean hive in winter to find a protected spot. When temperatures get low the queen’s body produces glycerol which keeps the cells from freezing. In the spring the queen is ready to lay eggs and start a new colony continuing her genetic line for a summer of reproducing, nectar gathering, and pollinating.
And some annual plants survive winter by producing seeds that will germinate in the moist grounds at the first signs of warm weather. Although this is common knowledge it is no less of an amazing phenomenon. That a seed can store genetics and energy to start anew after a heavy winter is another miracle of Mother Nature. On the surface this is a seemingly simple process but, in fact, it took millions of years of evolution for successful seed germination in harsh environments to be successful. This is just another example of the natural world’s propensity for tenacity.
Winter is cold, dark, and intimidating. Only the most hardy have adapted to survive in these northern climates. Although the clever adaptations are many they are all miraculous. Spring will bring the end of sleep for some, new life for many, and hope for all.
Written for www.wildramblings.com in November of 2010.