Worming Their Way Into Spring
During spring, when many birds, caribou, manatees and monarchs are traveling long distances, another migrant is moving, too—but this critter's whole journey can be measured in feet—or sometimes in inches! Earthworms spend the winter in the soil, often below the frostline. As warm spring rains and melted snow seep down, the soil at the top defrosts. Worms soon wiggle to the top. This isn’t a north-south migration, or even an east-west migration. It’s called a vertical migration.
During winter most worms stay in their burrows, prisoners below soil frozen hard as rock and topped by ice and snow. They are coiled into a slime-coated ball and go into a sleep-like state called estivation, which is similar to hibernation for bears. (The mucous, or slime, keeps the worms from drying out.) Worms will survive in frozen or dry soils by estivation until conditions improve, but not all kinds of earthworms make that downward journey to survive winter. Some kinds of earthworms lay their eggs in cocoons safe in the soil to hatch when conditions are right. Then they settle under leaf litter on top of the soil, where winter's cold makes them freeze and die.
But spring is coming! As the soil thaws down to the level of the estivating worms, their bodies start to work again and they start eating. During cool, moist days, they can often be found at the surface, where they become a handy food source for robins! But the hot sun often drives the worms back into the soil. Worms emerge at night, when the air is cool and moist. They feed on decaying organic matter on the soil surface. Have you seen your first earthworms yet? Be sure to report them by clicking on the owl button on any Journey North page!
How would the world look, sound, and feel if you lived at ground level or below? What if you couldn't control your body temperature or even shiver when you were cold, and you had no arms or legs and could only wiggle to move about? Check out our lesson that compares your body functions to a worm's! Then imagine you're a worm. What could you do on a day in your life when you don't get gobbled up by a robin? Find facts and fun here:
Robins eat worms, and plenty of them. The little worm in Gary Larson's book, There's a Hair in My Dirt: A Worm's Story, isn't happy with his lot at the bottom of the food chain. In an outburst at the worm family's table one day, the little worm yells, "Dirt for breakfast, dirt for lunch, and dirt for dinner! Dirt, dirt, dirt! And look--now there's even a hair in my dirt!" Read the book and enjoy these activities:
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