I wish to draw your attention to *The Serengeti Rules*, a recently released documentary film on keystone species and trophic cascades. Although the film is not exclusively about marine mammals, a significant part of it focuses on marine mammals and their associated ecosystems in the North Pacific Ocean and Bering Sea. The film comes in two flavors—a longer version (currently showing at various theaters in the United States and abroad) and a shorter television version that showed recently on PBS Nature (https://www.pbs.org/wnet/nature/the-serengeti-rules-41dfru/). Both versions build on seminal ideas of the late Robert T. Paine by tracing the work of four other scientists who followed in Paine’s footsteps—John Terborgh, Tony Sinclair, Mary Power, and me. This conceptual foundation provides a way of comparing marine mammals with coastal, fresh water, and terrestrial apex predators. Surprisingly, the challenges for their conservation have many overlaps. Although I was featured exclusive in the marine mammal portion of the film, many members of the marine mammal community were involved in the science of this film. I therefore wish to acknowledge the following people; J. F. Palmisano for discovery of the keystone role of sea otters in kelp forest ecosystems; D.F. Doak, M.T. Tinker, and T.M. Williams for discovery of the likely role of killer whale predation in the collapse of sea otters and coastal ecosystems in southwest Alaska; A.M. Springer and G.B. van Vliet for the initial discover of the role of whaling in the Sequential Megafaunal Collapse Hypothesis, and E.M. Danner, D.F. Doak, K.A. Forney, B. Pfister, and T.M. Williams for their contributions regarding the decline of sea otters and pinnipeds in southwest Alaska as initiated by industrial whaling. James A. Estes Department of Ecology and Evolutionary Biology University of California Santa Cruz, CA 95060 831-459-2820 jestes@ucsc.edu https://www.ibiology.org/ecology/apex-predators/