Earthworms Escaping Predation: A Disappearing Act

Background
If you were a worm trying to escape a hungry bird, what would your luck depend upon? Would the soil type make any difference? In this activity, students use worms to investigate how long it take a worm to get underground in various soil types, and to consider variables that might affect the time it takes.

Discuss where students have seen earthworms, and to comment on what the soil was like. (Depending upon age of your students, you may wish to discuss that soil is make of particles of sand, silt, and clay. Clay soil is very fine. Sandy soil has larger particles and feels gritty. Loam soil is a mixture of sand, clay, and organic matter--once-living leaves, twigs, stems, and parts of animals and plants. Loam is usually black.)
Form teams of students to collect soil from each of these places: a garden, a field, an empy lot, woods, and any other places they have observed earthworms.
Ask students to make predictions about which bucket worms will burrow and disappear the fastest and which bucket the slowest. What are the reasons for these predictions?
Print our data collection sheet and ask students to time and record the worms's burrowing into the soil of each bucket.
Check predictions. Ask students to brainstorm a list of variables that might affect the time it takes for a worm to disappear underground. (The ideas may include things such as soil type, worm type, moisture, compaction of soil, etc.)
Discuss: How could you find out how each of the variables affects the time it takes for the worm to go underground?

Worm Predators: American Woodcock and American Robin
(photos by J.A.Spendelow (l) and **Ann Cook** **(r).**