Northland Nature: Woolly bear caterpillars known as winter omens
Nov. 3—As we get to this time of autumn, the local wildlife are preparing to deal with the coming cold season. Their methods of handling the impending winter vary with different critters but can be summed up in four ways.
Some will leave the region where they grew up or spent the last months raising a family. This southbound migration is best seen among birds, as noted daily at Hawk Ridge. The migrants may go to a few states south of here, or perhaps all the way to Central or South America.
Birds are the best-known migrants, but other winged animals, bats and a few insects, also migrate. Though some insects, most notably monarch butterflies and green darner dragonflies, will migrate, a large number deal with winter in another way.
The adults are active in fall, lay eggs that will overwinter while they themselves will succumb to the cold. The protected eggs ensure the next generation in spring. This is what happens with grasshoppers, moths and most mosquitoes.
At this latitude, many wildlife will handle the cold by sleeping through it. Hibernation varies with those who partake it. We know that bears and woodchucks will fatten up in the fall to survive the winter. Others, like chipmunks, raccoons and skunks, wake occasionally. Insects, amphibians and reptiles are in deep hibernation or diapause.
And there are those that remain active. Many birds and mammals will winter here. With a change of diet and behavior, they survive the season of dark and cold.
Whatever their wintering method, they need to get prepared at this time. Sometimes we notice them preparing. It might be bears raiding feeders, mice trying to get into houses or insects on the move.
During the weeks of October and early November, it is common to see a little furry critter crossing over the roads, sidewalks or paths. These black and reddish-brown critters are well-known as woolly bear caterpillars.
Widespread and easy to see since they travel during the daytime, they are called by various names: woollybears, woolly bears, woolly worms and weather worms. They are frequently seen as they move their furry bodies, about 1 inch long, this time of year. Their bodies are completely hairy — black on both head and tail ends (may be hard to tell apart) and a patch of reddish-brown in the center.
Probably because they appear in fall, they tend to be seen as a harbinger of winter. Some say that the size of the black and reddish-brown patches tell us of the winter to come.
Caterpillars molt often as they grow and each molt has a different pattern, not likely for predicting weather. They hatch from eggs in late summer and grow through the following weeks. We see them now because they are also dealing with the coming winter.
Woolly bear caterpillars are the larvae form of a moth called the Isabella tiger moth. Though the adults are yellow, they are nocturnal and live only for a few weeks in summer. We know the caterpillars much better.
These larvae do not need to predict the weather to be amazing. Instead of dying or forming a cocoon, they go through winter in this caterpillar stage. Finding a secluded site under logs, rocks or leaves, they curl up and go dormant. Throughout the cold, they are protected by forming "anti-freeze" chemicals within their bodies.
In spring, they wake and thaw, feed and form a cocoon. Emerging in summer as the adult Isabella tiger moth. But at this time, we see them as they move about searching for the right place to spend winter.
