Presenter: William Oestreich (Stanford University)

Description:
Matching the timing of life history transitions with ecosystem phenology is critical for the survival of species undertaking long-distance migrations. As a result, whether and how migratory populations adjust timing of life history transitions in response to environmental variability are important questions in ecology and conservation. Yet the flexibility and drivers of life history transitions remain largely untested for migratory marine populations, which contend with the unique spatiotemporal dynamics and sensory conditions of marine ecosystems. Here, using an acoustic signature of blue whales’ regional population-level transition from foraging to breeding migration, we document significant interannual flexibility in the timing of this life history transition (spanning ~4 months) over a continuous 6-year study period. We further show that timing of this transition follows the oceanographic phenology of blue whales’ foraging habitat, with a later transition to breeding migration occurring in years with an earlier onset, later peak, and greater accumulation of biological productivity. These results indicate that blue whales use flexible cues, likely including individual sensing of foraging conditions and long-distance conspecific vocal signals, to match timing of this population-level life history transition with interannual oceanographic variability in their vast and dynamic foraging habitat. Blue whales’ transition to breeding migration and the associated acoustic signature can be considered an acoustic ecosystem indicator, providing useful real-time information to both resource managers and blue whales themselves. Preliminary agent-based model results suggest that this long-distance acoustic information aids blue whales in optimally timing their transition to migration. Further, the use of such flexible cues in timing a major life history transition may be key to the persistence of this endangered population facing the pressures of rapid environmental change.