Pinniped censuses at Año Nuevo, California, 1967-2017

Regular pinniped censuses at Año Nuevo Island, California, were initiated by our research group in 1967 to support studies of reproductive behavior of male elephant seals, Mirounga angustirostris. Research on elephant seals at the colony has continued since, expanding to cover female behavior, reproductive success, physiology and energetics, migrations and foraging, and more. The other species of pinnipeds, Steller sea lion (Eumetopias jubata), California sea lion (Zalophus californianus), and harbor seal (Phoca vitulina), have been the focus of additional studies. Censuses were collected to support the wide range of research, but population size of has been an important topic as the elephant seal population expanded. We described the initial expansion to the mainland in 1975, and in 2011 described details of long-term growth and then stabilization of the breeding elephant seal population over the entire colony. Año Nuevo has also been central to understanding the entire northern elephant seal population, which has recovered from a remnant population in Mexico after overhunting and continues to grow.