The wolf today inspires polarized emotions. It is viewed by some as a slavering, rapacious killing machine; by others, as the noble symbol of a lost wilderness. In the fascinating Decade of the Wolf: Returning the Wild to Yellowstone, biologist Douglas Smith and nature writer Gary Ferguson seek to sort myth from reality. They describe wolves' actual lives and habits as well as the effects they've had upon the ecosystem of the national park since their reintroduction in 1995.

Those effects are myriad. Willows flourish, riparian zones revive, pronghorn fawns stand a better chance of growing up, and eagles, ravens and magpies feast — all, the authors believe, due to the restoration of wolves to Yellowstone. Smith, head of the Yellowstone Wolf Recovery Project, explains that when wolves are present, elk avoid places with limited visibility, such as brushy riverbanks. Without elk lounging in riparian areas, willow shoots grow and beaver ponds appear. Meanwhile, as wolf packs kill elk and bison, at least 14 other species also thrive by scavenging the carcasses. But coyotes decrease in number, and their prey, such as the pronghorn, rebounds.

The Yellowstone packs regularly draw crowds of awed "wolf groupies." But other people remain violently opposed to wolf reintroduction, illegally shooting or poisoning the animals. Wolves do kill livestock, but the authors argue that they are hated far out of proportion to any damage they cause — perhaps as a remnant of old superstitions that portrayed them as satanic. In the end, they are neither good nor evil, just wild animals facing an uncertain future.