A visit to a remote national park that is the site of the longest uninterrupted predator-prey study in history.Following the pattern of other entries in the much-honored Scientists in the Field series, Castaldo and Heim introduce several biologists and other researchers working at Isle Royale, a group of islands on Lake Superior, with portraits and short descriptions of their work and interests. Castaldo adds historical context and observations gleaned from a decadeslong study of how rising and falling populations of local wolves and their main prey, moose, affect the unusually isolated area's entire ecosystem. She also offers an evenhanded view of a controversial recent project: After the wolf population nearly went extinct, in an attempt to restore the predator-prey balance artificially, scientists imported wolves from outside in the hopes that they would breed. Castaldo leaves it for reflective readers to decide whether that is responsible conservation or unscientific meddling with natural patterns. As in other titles in the series, the big, bright color photos are a strong point, and even though the closest Castaldo or Heim gets to a wolf or a moose on their expedition is some piles of scat, stock wildlife close-ups are seamlessly mixed in with views of rugged woodlands, rocky shores, and outdoorsy workspaces, notably, a large and neatly arranged moose boneyard. The researchers portrayed appear to be White.Stimulating reading for young naturalists and eco-activists. (maps, glossary, further reading, source notes, index) (Nonfiction. 10-13)