Food Web Activity: What Would Happen If the Wolves Disappeared?

A food chain is a line: grass, rabbit, fox. A food web is the truth: many chains tangled together. This yarn activity makes the tangle physical, and it makes students feel what happens when one part is removed.

What you need

A ball of yarn (at least 30 m)
Index cards, one species per card, with a loop of string to wear
Scissors (teacher only)
Chart paper and markers

Set up the web

Choose an ecosystem, such as a northern forest or a prairie. Give each student a species card. For a northern forest, a set might include wolf, deer, moose, rabbit, fox, berries, grass, trees, mice, owls, mushrooms and insects. Include producers (plants), herbivores, carnivores and decomposers.

Students stand in a circle holding their cards.

Build the web

The student with “grass” holds the end of the yarn.
Ask: “Who eats grass?” The student playing the rabbit raises a hand. The yarn is passed to the rabbit while the grass holder keeps hold.
Ask: “Who eats rabbit?” The yarn goes to the fox, the owl or the wolf, while each previous holder keeps hold.
Keep going until every species is connected to every species it eats or is eaten by, using as many yarn crossings as needed.

The result is a tangled web. Stand back and look at it.

Remove one species

Choose one, such as the wolf. The wolf student drops their yarn (the teacher can cut it). Everyone who feels a tug raises a hand. Those people are directly affected. Now ask: “What would happen to them? Who would be affected next?”

Discuss predictions:

Fewer wolves means more deer and moose to eat.
More deer eat more plants, so there are fewer berries and young trees.
Fewer berries means less food for other animals, such as mice and birds.

Students quickly discover that the effects spread much farther than the wolf’s direct neighbours.

Test other removals

Try removing something at the bottom, such as grass, or a decomposer. What’s different? Removing the plants affects nearly everyone. Removing decomposers affects the nutrients returning to the soil, a slower, hidden effect.

What to take away

No species lives alone.
Producers capture the Sun’s energy, and consumers pass it along.
Predators can control the numbers of the animals they eat, which in turn affects plants.
It’s hard to predict every effect, and real ecosystems are more complex than any model.

Be careful about oversimplifying

This is a model. Real animals eat many things, populations adjust over time, and scientists study cases carefully before drawing conclusions. Say so, and invite students to ask what evidence would settle a question.

Try What would happen if the wolves disappeared?, with a teacher guide and student sheet, and the rest of Food Webs: Who Eats Whom?, including Who cleans up? and Can we count the life under a log? Sign up for three lessons free.