Each animal (plus one plant) is introduced primarily in terms of its crucial ecological role as a keystone species. In Sea Otters, for example, readers learn about the environmental importance of kelp forests, then discover the otters’ unique ability to hunt the sea urchins that feed on kelp. The second half of each book looks at threats to the keystone species, potential dangers if they can’t fill their roles, and efforts by humans to protect them. Clearly written text covers various ways that these species fit into their ecosystems. Prairie dogs, for instance, keep soil healthy, aiding grazers, birds, and insects, and also serve as the single food source for black-footed ferrets (Prairie Dogs). Large photographs depict the environments and the ways that animals interact with it. A final spread offers tips for readers to help preserve the species. VERDICT Clear, well-organized introductions to keystone species and their habitats.