Our results demonstrate that blue whales track the long-term average phenology of the spring/summer phytoplankton bloom as they forage progressively farther north along the west coast of North America, signifying that memory plays an important role in the movement decisions of these long-lived animals. In other words, we find that blue whales surf climatological resource waves, using memory to track shifting hotspots of predictable and high-quality resources. Long-term memory has been shown to be a strong driver of migration patterns across taxa (17, 22), and in some cases a stronger driver than proximate cues. For example, the migration direction of zebra during long-distance migrations in southern Africa was predicted significantly better by memory (modeled as tracking of past average conditions) than by tracking of contemporaneous resource waves (17). Similarly, several species of long-distance avian migrants have been shown to track decadal averages of vegetation conditions (18). In addition, many migratory megafauna display extreme individual-level fidelity to their interannual migration routes (56⇓–58). Our study indicates that an interplay between both long-term memory and resource tracking shapes the long-distance migrations of marine megafauna.