James A. Estes, Ph.D.

Research

James A. Estes, an international expert on sea otters and a specialist in the critical role of apex predators in the marine environment, died in 2025. Estes was a professor at the University of California, Santa Cruz. He used his Pew fellowship to investigate whether industrial whaling in the North Pacific Ocean following World War II could provide an explanation for the disruption of this ecosystem. He suspected that the selective removal of large whales from the North Pacific left their foremost natural predator, the killer whale, without one of its significant food sources. Estes organized an international symposium on the influence of whales and whaling on ocean ecosystems that was held in April 2003 in Santa Cruz, California. More than 50 experts from around the world attended. Although the problem is both complex and highly controversial, Estes and his colleagues provided a credible argument that whaling was a significant driver in the megafaunal collapse and that the restoration of great whale stocks to something resembling pre-exploitation levels might be necessary to restore this ecosystem.