Our first really cold spell of the season is upon us. NOAA’s weather map this week showed a color I rarely see in “our neck of the woods”. A light, almost translucent blue color that ominously matches my memory of Snow Miser’s long fingers in the 1974 Bass/Rankin stop-motion animation film A Year Without A Santa Claus. Our neighbors to the northeast as well as Michigan, Wisconsin, Minnesota, Indiana, and Ohio are also in this icy clutch of blue on the map, which represents a wind chill advisory. It is only 9:00 am as I write and the chickens’ water, changed at 7 am, has already frozen solid. I suspect I will be making several trips with fresh water today. So, yes, baby, it’s cold out there.
I always marvel at how animals survive this kind of weather. Of course, some hibernate, and some can stay underground (below four feet the temperature stays around 55° F). What about the animals that must venture out to find food? When I went out to get some wood off the porch, I heard the distinctive tapping of a woodpecker looking for food. It took me a minute to find him, and in that minute my fingers, with gloves on, got painfully cold. It was a pileated woodpecker. Wow! Out there looking for insects in the cold air, and in a manner that does not at all seem painless. I prefer to catch my insects by hand!
Animals have numerous adaptations for surviving winter weather. An adaptation can be behavioral, structural, or physiological. And within the category of behavioral adaptations – at which we humans excel – the adaptation can be learned or instinctual. For example, blinking is an instinctual behavior/response to something coming toward our eye. Birds coming to our feeders, and especially the ones stealing cat food from my side porch, represent learned behavior. In this latter example, the behavior is also quite brave as the cats’ food bowls are very close to the cats’ sleeping bins. I guess the benefit – a high protein, easy food score – outweighs the risk of being caught by a cat. And it seems they are right because my cats are older and rather lazy, though I still see Thingy bringing home mice occasionally from the lower field.
One of the best-known behavioral adaptations to winter weather (or food shortage) is migration. While I think this behavior is amazing, and scientists are still learning about the cues animals use, it is the animals that stay behind and remain active that really amaze me. It is much easier to imagine spending the winter somewhere warm, if not the onerous task of getting there, than it is to imagine spending the winter living in the subterranean or the subnivean zone and needing to venture out for food. Of course, I can’t grow a thicker layer of fur, or lower my body temperature and metabolism. I don’t need to change my skin or hair color to hide from predators in the snowy world. And that’s not just because of climate change; I couldn’t do that even before the winters where I live started receiving less snow.
I have often read where people feel that science takes the wonder out of nature. I emphatically disagree. The more I learn about nature the more awestruck I become and the more questions I have. Here are just a few wows I have learned recently:
Delayed fertilization in bats. Copulation occurs in the late summer and early fall when the male bats are at their fittest, not in the spring when they would be at their weakest. Fertilization occurs as soon as bats emerge from dormancy. It is thought that this gives bats an advantage to develop fully before the next cycle of dormancy.
Delayed implantation in bear, fisher, marten, river otter, mink, and long-tailed weasel. The further development of a fertilized blastocyst is arrested until conditions are suitable for healthy development and birth.
Communal denning. Snakes, squirrels, raccoons, and opossums are known to share dens with each other and with other species, sometimes even with other animals that would be a predator or prey under warmer conditions.
White winter hair not only acts to help camouflage, but also has more air spaces, therefore more insulative properties, because of the lack of melanin.
Snowshoe hares and weasels do not accumulate winter fat to stay warm. The hares need to stay lightweight to help escape predators in the snow, even though those big feet are acting as snowshoes. Weasels need to stay slim to enter the small tunnels of rodents, their main winter meal. Weasels do not even keep a winter den, but rather eat in the den of the prey they have caught – nature’s example of a progressive dinner!
The adaptations I was already familiar with: variations of hibernation, torpor, and aestivation; and acquiring a thick layer of fat, are no less amazing to me. In cold weather, heat becomes the currency of survival. Humans are not the most efficient at creating and storing heat despite our numerous and arguably ingenious behavioral adaptations to survive in the cold. The igloo is probably the most efficient dwelling we have ever created. We cannot maintain our body temperature well without burning external sources of stored energy. I cannot structurally or physiologically adapt to cold temperatures, nor can any of us. We have circumnavigated the evolutionary processes in place before we started wearing clothes and migrating all over the world, building huge shelters that are much harder to keep warm than an underground chipmunk burrow. I do feel more comfortable in my den than I imagine I could in a chipmunk burrow for the winter. But do we really understand all the social and ecological costs of our need for heat? Because I worry about our consumption of energy, from both a global perspective and my family’s finances, I keep the thermostat on 54° F during the day and 60 ° F at night, and I keep the woodstove burning. I add layers of wool instead of fat (well, maybe a little fat), and wander outside often to try to catch a glimpse of animals busily surviving the cold. I think I even get a little warmth from the “magic” I find.