Monday, November 2, 2009

Rural Delivery: Cold Hardening

by Michael Hofferber. Copyright © 1996. All rights reserved.

Hard frost again last night. My footsteps leave dark impressions on the ground. The breath of the cows rises in clouds as they huddle together like football players at Soldier Field on a December Sunday.

Fewer grasshoppers now, I notice. They used to scatter through the wheat stubble on my approach. Only a few stragglers remain. The rest have died or gone off to hide from winter.

The crisp night is giving way to a warm morning glow. It will be an "Indian Summer" sort of day, the kind we missed out on last year when winter dropped in early. Some of our coldest weather came in November rather than January, where it belongs.

Most of nature depends on a steady progression of seasons.

These cool nights encourage the growth of fat and fur on dogs, cats, horses and most other warm-blooded critters. My beard and waistline, too, seem to grow more readily this time of year. By winter solstice, or late December, we'll be well acclimated to the cold.

Reptiles, insects and other creatures make similar adjustments. Many bury themselves in the most protected spot they can find and slip into a deep torpor, like hibernation, which lasts throughout the winter.

Even no-see-ems -- those nearly invisible biting midges that infiltrate lawns and campsites, nibbling at whatever skin they latch onto -- have a nifty wintertime adaptation. Their bodies start producing a protein this time of year that acts as a sort of antifreeze.

Scientists don't know exactly how the no-see-em, or Culicoides variipennis sonorensis as they call it, accomplishes this winterization. They have discovered that if the insect is suddenly exposed to a temperature of 14 degrees for two hours it will die. But if the no-see-um is first exposed to 41 degrees for an hour, it can survive at 14 degrees for up to three days.

This wintertime acclimation, known as "cold hardening," is also found in the pesky fruit fly and the common house fly. It is one reason why a hard winter won't always kill off an insect population and the diseases it carries.

My own cold hardening begins with snow tires on the truck, weather-stripping around the windows and doors, and a couple cords of firewood split and stacked. There's still gloves and boots to buy, trees to prune, feed to stock up on, and garden beds to mulch. I don't have any antifreeze proteins in my system that I know of, but I've noticed that 30 degrees isn't as chilling as it was a couple weeks ago.

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