Bibliografi hlm, 188-194., ; Ilus., ; indeks
Wolves, like the one shown on the front cover guarding a skeleton of a caribou, were close to extinction in the 1930s. In Yellowstone National Park, the removal of the wolves had ripple effects on the ecosystem. Without a natural predator, the elk population increased, and the preferred food source of the elks— cottonwood and willow trees—began to dwindle. With fewer trees to stabilize the …