Adjusting to Winter

ArrayDecember 20, 2018 at 9:38 am

By Sarah Spencer, Wildlife Biologist As we approach the winter solstice, the days get shorter, temperatures drop, and precipitation starts falling in the form of snow. To the wildlife here in Maine, it’s a transition they’ve been preparing for since day length began to shorten back in June. Wildlife are incredibly well prepared to deal with these changes, whether it’s by migration, hibernation, torpor, or adapting their physiology and behavior. [caption id="attachment_3224" align="alignright" width="300"] Monarchs of eastern North America migrate south to overwinter in the Sierra Madre Mountains of Mexico.[/caption] Many species of birds migrate south toward warmer climates to overwinter, but did you know that monarch butterflies also migrate southward? Monarchs of eastern North American migrate south to overwinter in the Sierra Madre Mountains of Mexico. Interestingly, it takes several generations of monarchs to make the northward migration, but a single generation migrates from the northern extent of the range back to their wintering grounds in Mexico. Maine’s true hibernators reduce metabolic activity, reduce heart and breathing rates, and significantly drop their body temperatures. This group includes bumble bees, in which the mated queens hibernate; wood turtles, which hibernate underwater in sheltered areas of rivers; and several species of bats, which hibernate in caves, tree cavities, buildings, and old wells. Black bears experience something slightly different, termed torpor, which is when body temperatures don’t drop significantly as they do true hibernation. For non-migratory species and those which don’t hibernate or go into a state of torpor, there are a variety of adaptations to help them through the winter. Deer and moose have a winter coat of hollow hairs which help conserve energy by insulating their bodies against heat loss. Deer will also “yard”, or gather in groups where softwood shelter protects them from the harsh winter, and they pack down trails through the snow to reduce the energy it takes to move through a snowy landscape. Snowshoe hare molt their brown summer coat for a white winter coat allowing them to blend into their surroundings when snow is present, while their large fur-covered hind feet are well-adapted to moving in deep snow. Perhaps one of the most amazing feats of winter survival is that of the Golden-crowned Kinglet. This bird weighs approximately twice that of a Ruby-throated Hummingbird, but relies on nocturnal hypothermia while huddling together in small groups in abandoned squirrel nests to survive temperatures as low as -40°F! As the season turns, you can make your own observations of the wildlife in your backyard or elsewhere on Maine's landscape as they prepare as well.