Killed for their horns, Africa's black rhinos face extinction. The species has made a comeback with human help. But hunters and lack of space still threaten its survival. The Animals in Danger series presents Black Rhinos, an all-around guide to the fascinating two-horned giant. Cutting-edge science helps tell the inside story of the black rhino's habits and personality. Eyewitness reports offer a look at the work to save the species. In addition, images and extra features like maps and a glossary help readers understand black rhinos and how human actions affect the animal's present and future.