Ernest P. Walker (1891-1969) began work on Mammals of the World in the early 1930s, when he became assistant director of the National Zoo in Washington. His work reflected an unequaled store of knowledge about the world's mammals.

Ronald M. Nowak is the author of the fifth and sixth editions of Walker's Mammals of the World. His other works on mammalogy include North American Quaternary Canis and several parts of the National Geographic Society's Wild Animals of North America, for which he also was editorial consultant. He received a Ph.D. in biology from the University of Kansas in 1973 and was staff mammalogist at the former Office of Endangered Species, U.S. Fish and Wildlife Service, from 1974 to 1987. He served as an Air Force officer for four years and is a private pilot.

Marine mammals are among the most fascinating, and most watched, of the earth's many animal species. Some, such as dolphins, are known for their intelligence, friendliness toward humans, and surprisingly sophisticated social behavior. In addition, all these animals are sources of fascination for the special adaptations they have undergone for life in and around the water, for their unique methods of communication ("whale song"), and for the endangered status of many species. This comprehensive guide includes scientific and common names, the number and distribution of species, measurements and physical traits, habitat, daily and seasonal activity, population dynamics, home range, social life, reproduction, longevity, and status of threatened species. A foreword by John E. Heyning is engagingly written for the general reader, while a more detailed and substantive introduction by Randall R. Reeves and Brent S. Stewart discusses issues in greater depth for the specialist.