Fantasy is blended with environmental concerns in this mildly affecting story about a kangaroo rat who speaks up for her threatened home. When scientists who have captured Leaper attach her to a computer that tracks her sounds, they are so shocked to hear her announce her name that they pay no attention to her warnings of a ""monster"" attacking her desert habitat. Julian, an unsure 12-year-old lab worker, gets Leaper's message; his efforts to so something about it lead him into the desert, where he finds that motorbikes, like his own, are the culprits. Julian almost dies in a flash flood but also acquires a goal: to become a naturalist rather than exploit nature as his employers do. Though Julian and Leaper are sketchily portrayed, they are the most fully rounded characters here; the scientists are merely ciphers, set up to be knocked down in the course of the schematic, predictable plot. But at least the descriptions of desert life are moving. Illustrations not seen.