This book is part of an ongoing series created by the United States Department of the Interior's Fish and Wildlife Service, which publishes scientific investigations related to birds, mammals, reptiles, and amphibians. This particular installment delves into the diverse mammalian fauna of Costa Rica's La Selva-Braulio Carrillo complex, an area spanning tropical wet forests, cloud forests, and various transitional zones. The book's team of researchers conducted mammal surveys along an elevational transect from lowland to montane habitats to determine species distributions and relative abundance. With support from the National Geographic Society, the Rice Foundation, and the Organization for Tropical Studies, they documented the rich mammalian diversity of the region, encompassing species of bats, rodents, carnivores, marsupials, edentates, artiodactyls, primates, rabbits, shrews, and perissodactyls. The author emphasizes the importance of the region as a refuge for a variety of species, especially those requiring large, undisturbed habitat areas. The book serves as a valuable resource for mammalogists, ecologists, and conservationists, providing a comprehensive overview of the mammalian fauna of this ecologically significant region and highlighting the need for continued protection of such diverse and fragile ecosystems.