Half-century whale census shows rising solo sightings and longer calving gaps

For five decades scientists have flown over the Great Australian Bight to monitor the migratory and breeding habits of the endangered southern right whale. This year’s count, led by Murdoch University senior researcher Joshua Smith, tallied 520 whales, including 235 mother-calf pairs, a decline from last year’s 646 sightings and 304 calves. The survey also noted roughly 50 unaccompanied whales, indicating a rise in solitary individuals.

Analysis of the long-term record shows the species’ calving cycle, once every three to four years, is now lengthening to about five years, reflecting a stagnating population. Chief scientist Claire Charlton attributes the shift to warming ocean temperatures that diminish krill and sea-lice, reducing the whales’ food supply and prompting delayed breeding. She warns that similar declines are evident in southeastern Australian populations, where mother-calf sightings are scarce.