targeted old or sick animals. As a result,
the rest of the prey population was
healthy. By hunting, wolves also kept prey
populations from growing too fast.
Without wolves, elk populations in
Yellowstone soared. Elk overgrazed on
trees, shrubs, and other plants. Their
grazing caused fewer young trees to grow.
This change affected many other species.
Songbirds had fewer spots to nest.
Wild elk graze in Yellowstone National Park.
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