Rick McIntyre is a wolf behaviorist who has spent more than forty years watching wild wolves in America's national parks, twenty-eight of those years in Yellowstone, where he has accumulated over 100,000 wolf sightings and educated the public about the park's wolves. He is retired from the National Park Service and is currently a faculty affiliate at the University of Montana.

Frans de Waal was a primatologist and ethologist. He was the Charles Howard Candler Professor of Primate Behavior at Emory University in Atlanta, Georgia, director of the Living Links Center at the Yerkes National Primate Research Center at Emory, and author of numerous books including Mama's Last Hug and Different: Gender Through the Eyes of a Primatologist.