The Winter of Our Lives
Our animal relatives have much to teach us about winter as a season of rest and renewal. Some of us might associate hibernation as a retreat from reality and torpor as a state of apathy and laziness. However, in her memoir Wintering, Katherine May likens difficult times in our lives to winter and writes, “Plants and animals don’t fight the winter; they don’t pretend it’s not happening and attempt to live the same lives that they lived in the summer. They prepare. They adapt. They perform extraordinary acts of metamorphosis to get them through. Winter is a time of withdrawing from the world, maximizing scant resources, carrying out acts of brutal efficiency and vanishing from sight; but that’s where the transformation occurs. Winter is not the death of the life cycle, but its crucible.”
A Torpor Over the Forest
As the temperatures become consistently colder, the forest’s animals begin to slow down and prepare for winter. Deer and moose grow thick coats, decrease movement, and start foraging for food. Squirrels hunt for nuts and seeds to store in a cache while bulking up their nests. Birds begin migrating to their warmer winter destination. Beavers submerge limbs with leaves near their well-insulated lodge so they can feed on them throughout the winter.
Degrees of Hibernation
Some forest animals opt out of all that cold weather activity. They sleep. This long winter’s nap is commonly known as hibernation, and there is a variation called “torpor.” Both represent a depressed metabolic state, but there are key differences.
Hibernation is longer term, lasting weeks or months. During that time, metabolism, body temperature, and heart rate decrease dramatically, breathing becomes shallow, and the animal relies on stored fat for nutrition. Animals enter hibernation voluntarily to prepare for the cold winter months and lack of food.
Winter Bear Necessities
Ironically, the animal we most associate with hibernation–the bear–enters a state of torpor, along with smaller mammals such as mice and chipmunks. Torpor’s decreased metabolic state is much shorter, lasting hours to days.
While the bear’s metabolism slows down in torpor, it’s not nearly as marked as in true hibernation. For animals that enter a torpor state, it’s an involuntary response to colder weather. The black bear needs temperatures consistently below 40 degrees to enter torpor, and there’s no guarantee they will stay there if temperatures start to climb.
Do Not Disturb
In this lighter state of unconsciousness, a bear in torpor can be easily roused by noise or disturbance. While we might have images of bears retreating to caves for their winter’s rest, there’s a housing shortage of those structures and not enough to go around! Bears ride out their torpor under fallen trees and rocky crevices, making GMF’s glacial erratics prime winter real estate. In a pinch, bears may create a shallow nest in the ground or a hollow log and cover themselves with a blanket of leaves, moss, and other loose forest ground cover.
Cold-Blooded Sleepers
The equivalent of hibernation for turtles and frogs is known as brumation. This involves decreased body temperature, heart rate, and circulation during the colder months. Frogs and turtles hibernate at the bottom of GMF’s ponds, covered in mud, waiting out the winter and dreaming of warmer temperatures. Glycogen in their blood allows them to absorb oxygen in these watery beds.
Rising Spring
When temperatures rise in the spring, GMF’s animals begin to rouse and lethargically emerge from hibernation and torpor, confused, slow, and disoriented. They quickly acclimate and begin a quest for food and water to replenish their reserves, depleted over the cold winter months. Heavier coats grown to preserve heat are now shed in preparation for the warmer months. Bears, capable of giving birth during torpor, prioritize the feeding and safety of their cubs. And with the end of hibernation also comes the mating season in the forest when new energy and life begin in earnest.
