Wolves reproduce. They get energy by eating elk. Elk reproduce. They get energy by eating grass. All lose a bit of energy at each time step. Any wolf or elk whose enegy goes below zero dies. Grass grows over time, but is cut down by elk eating it. This is a predator-prey ecology. Including grass, in theory, helps stabilize the ecology.
Elk and wolves oscillate in numbers. The Scratch limit of 300 clones puts a big limitation on this model.
