Climate crisis linked to fall in southern right whale birth rates as researchers raise warning signal'

"After decades of recovery, southern right whales are showing signs of a climate-driven decline in breeding rates, which scientists say is a warning signal about changes in the Southern Ocean. After being hunted to near extinction by commercial whaling in the 19th and 20th centuries, southern right whales remained endangered in Australia. But long-term monitoring has revealed a worrying slowdown in breeding rates since 2017. Instead of giving birth to a calf every three years, southern right whales have shifted to four-year or five-year cycles, says Dr Claire Charlton, a marine biologist and the director of Current Environmental."

"For more than three decades, scientists have used photo identification data collected at the Great Australian Bight to study the species, identifying individuals by unique patterns of a type of callus, called callosities, and tracking their migrations and breeding behaviour over time. Charlton, who leads the right whale program in the Great Australian Bight, says southern right whales are magnificent animals just the sheer size of them, and the fact that they live for 150 years. They feed in Antarctic and sub-Antarctic waters during our summertime, and then migrate up to our coasts during winter. The whales come every year to breed, mate, rest and socialise."

Southern right whales recovered for decades after near-extinction from 19th–20th century commercial whaling but now show a decline in breeding rates. Long-term photo-identification at the Great Australian Bight has tracked individuals by callosity patterns and revealed a slowdown in calving since 2017, with intervals increasing from three years to four or five. The whales feed in Antarctic and sub-Antarctic waters in summer and migrate to coastal breeding grounds in winter. Calving-interval data spanning 35 years correlate breeding rates with sea-ice extent, marine heatwave prevalence, prey availability and other Antarctic environmental changes, implicating climate-driven impacts on foraging.

Read at www.theguardian.com