By Elizabeth Bassett
Short of getting on an airplane, how do we cope with winter? Crank up the woodstove, invest in a therapy light, strap on winter traction devices….? Critters have some remarkable strategies. Read on!
Surviving winter (without a wood stove)
How do animals survive the rigors of a northern winter? Some become dormant or hibernate; many birds and butterflies migrate; others simply persevere, searching for food and shelter in the snow, a stonewall or your compost heap.
Warm-blooded mammals have little temperature flexibility. They must maintain a narrow range of body temperature in extraordinary swings of outdoor weather. Few animals actually hibernate, a deep, long-lasting sleep in which the body temperature lowers and heart rate plummets. Bats, the jumping mouse, and the woodchuck are among true hibernators. Come spring, the animals’ heartbeats accelerate and their body temperatures rise until they become alert again.
Dormant animals are more active, sleeping and waking intermittently, in burrows, tree cavities, caves and other shelters from wind and cold. On warm days they may venture out in search of food. Black bears are dormant. Raccoons, skunks and chipmunks also may experience some lowering of body temperature but not to the degree of the hibernators.
The majority of local mammals do what too many humans do: they accumulate an extra layer of fat and muddle through. Deer grow hollow hairs to retain additional body heat. Fur coats thicken. Snowshoe hares and weasels turn white for camouflage against the snow. Grouse grow comb-like bristles on their toes that serve as snowshoes while extra fur serves a similar purpose for the snowshoe hare.
What becomes of pond dwellers? Unable to regulate their body temperatures, cold-blooded animals slow down, their activities and metabolism stopping as they slumber through the cold with minimal needs. They generally survive if they are not encased in solid ice. Protected beneath the ice in water that never freezes, these creatures are insulated from temperatures that may plunge below zero.
Amphibians, such as frogs and toads, may sleep through winter on land or lay eggs that will hatch in the spring whether or not they survive.
Steve Faccio, a scientist at the Vermont Center on Ecostudies, attached radio-signaling tags to salamanders. (If there is a video of this I want to see it!) With a radio receiver and antenna, Faccio was able to monitor salamanders’ movements and locations. Following the “pinging” sound, Faccio crawled on hands and knees until he pinpointed the exact location. But there was no visible salamander! However, beneath the leaf litter and rotting logs a series of narrow, branching tunnels held the prize; Faccio moved just a few leaves and there was the salamander, peering out from a tunnel opening!
As fall temperatures plunged so did the salamanders, seeking more vertical tunnels leading deeper underground. By November Faccio had lost the radio signals, which travel only two or three feet, as the salamanders had descended below the frost line to escape from winter. As salamanders cannot dig, they use shrew, mouse and chipmunk tunnels for refuge. Tunnels are so crucial to them that Faccio could predict areas in the forest that would be inhabited by the salamanders simply by the density of mammal tunnels. With no small mammals, salamanders were not to be found!
Come spring salamanders will crawl to vernal pools, like the one that our team monitors at Raven Ridge. Even before the last ice has melted, salamanders, as well as frogs, will lay jelly-like masses of fertilized eggs as a new generation is launched.
Winter confinement suits beavers; they can sometimes be heard chatting in the lodge while they groom each other’s fur with special waterproofing oil. Their lodge is a platform of sticks and saplings covered with a dome-shaped mound. A carpet of shredded plants allows water to drain through the floor. Underwater entrances keep the beavers’ home safe from predators. Winter food rafts, leafy branches anchored to the pond bottom, are also protected by water and ice.
Climate change dilemmas
In the fall weasels and snowshoe hares trade their summer brown and red pelts for winter white. Thicker than their summer fur, seasonal cloaks not only keep them warm but also provide camouflage against predator and prey in the snow.
But what if there is no snow? Unfortunately for such critters, transformation of their winter fur is triggered not by temperature but by diminishing hours of daylight. If winter is warm or snow-free, white animals with an extra-warm coat may overheat and be more vulnerable to predators. They may also be more visible to their prey in a brown and gray landscape. Neither adaptation enhances survival of the species.
The State of Vermont also depends on winter. Winter sports participants—those who ski, board, snowmobile, ice skate—contribute to the financial well-being of our state coffers. For that reason alone Vermont needs a real winter!