Climate-driven reproductive decline in Southern right whales

Reproductive success and abundance trends in migratory baleen whales are linked to body condition and foraging success, making them vulnerable to changes in prey availability which is influenced by climate variation. Southern right whales (Eubalaena australis), a sentinel species for climate change, offer critical insight into Southern Ocean health. Using over three decades (1991–2024) of photo-identification data collected in southwest Australia, we document a significant decline in reproductive output driving a slowed rate of population increase in the last decade. Cross-correlation and principal component analyses reveal that prolonged calving intervals coincide with declining Antarctic Sea ice concentration, persistent positive Antarctic Oscillation, and increases in surface chlorophyll-a, signalling broader ecosystem shifts. These findings add to global evidence of the sensitivity of southern right whales to climate variability in their offshore foraging grounds. This reproductive decline represents a threshold warning for the species and highlights the need for coordinated conservation efforts in the Southern Ocean, in the face of anthropogenic climate change.