A population’s ability to cope with environmental change is influenced by the cumulative behavioral and fitness consequences of individual habitat selection strategies. Site fidelity is theorized to confer a fitness advantage in unpredictable environments over long timescales, yet may be maladaptive in environments undergoing long-term change. To date, a shortage of long-term datasets that combine movement and performance data has limited understanding of the relative short- and long-term benefits of site fidelity, and the effects of different climate conditions on these trade-offs. We brought together a 10-year satellite tracking dataset on northern elephant seal (Mirounga angustirostris) migratory movements, individual mass gain metrics, and oceanographic data to examine a) the long-term benefits of site fidelity, b) the relative benefits of site fidelity under different climate conditions represented by the Pacific Decadal Oscillation (PDO) Index, and c) the variability of oceanographic conditions characterizing foraging areas. We developed a site fidelity index to quantify the spatial consistency of migration patterns for individuals tracked over multiple years.
Our results reveal two markedly different habitat selection strategies within the population: a high site fidelity strategy facilitating moderate rewards and low risk, and a low site fidelity strategy facilitating potentially high rewards and high risk. Moreover, we show that large-scale climate conditions mediate the relative success of these strategies. Individuals with high site fidelity outperformed individuals with low site fidelity under neutral climate conditions (p <0.05), had lower interannual variation in their mass gain with site fidelity index explaining 68% of the variability observed, and used areas that had relatively stable resources over time. In contrast, individuals with low site fidelity performed best during positive phases of the PDO (p<0.05), had higher variation in mass gain among years, and foraged in areas with less habitat predictability. Our findings suggest that site fidelity is beneficial over long timescales by yielding reliable success across years, but given that climate variability is increasing in the North Pacific, this strategic advantage may be reduced as a result of long-term environmental change. By empirically testing the effects of climate variability on habitat selection strategies, our study offers a first glimpse into the behavioral and adaptive responses of marine predators to new climate regimes.