Steller sea lion natal rookeries (dots) sampled in this study. Pups from four regions were included: eastern Russia (blues), Aleutian Islands (greens), Gulf of Alaska (purples), and Southeast Alaska (aquas). The 12 subpopulations represented are color coded in different shades of the regional color. Within the USA, the designation at Cape Suckling separates the western and eastern Distinct Population Segments at 144° longitude.