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🇦🇺 Australia /Environment & Climate

50 Years of Whale Surveys Reveal Longer Gaps Between Southern Right Whale Births

From ABC Australia · () English

Translated from English and summarized by DistantNews. Read the original for the full story.

At a glance

News Named sources Context piece
  • Researchers recorded 520 southern right whales, including 235 cow-calf pairs, during this year’s survey from Western Australia to South Australia.
  • The count fell from last year’s 646 whales, while individual sightings declined 20% compared with a decade ago.
  • Long-term data indicate that calving intervals have lengthened from roughly three to four years to about five years, although protected areas in the Great Australian Bight continue to support strong gatherings.

For half a century, researchers have followed southern right whales along Australia’s southern coast, tracking their movement from Fremantle in Western Australia to Ceduna on South Australia’s far west coast. This year’s census recorded 520 whales across the south-west, including 235 mother-and-calf pairs.

Since 2011, there has been a stalling in the population.

· Joshua SmithThe Murdoch University researcher described the long-term population trend.

The result was lower than last year’s count of 646 individual whales and 304 calves. Individual sightings also fell by 20 percent compared with a decade ago. “Since 2011, there has been a stalling in the population,” said Joshua Smith, a senior researcher at Murdoch University who has led the aerial survey since 2018.

The Great Australian Bight still produced a strong result in protected waters. Claire Charlton, chief scientist with the Australian Right Whale Research Program, recorded 61 mother-calf pairs from land-based monitoring near the head of the Bight Commonwealth Marine Park and the Yalata Indigenous Protected Area. That represented more than 30 percent of the south-west total. “It’s a conservation success story for the marine park,” Charlton said.

It’s a conservation success story for the marine park.

· Claire CharltonThe Australian Right Whale Research Program chief scientist discussed strong mother-calf numbers in the protected Great Australian Bight.

The census also counted about 50 whales without calves. Traditional calving sanctuaries, including the Head of Bight and Israelite Bay in Western Australia, remained active, but Smith described overall activity as unusually quiet.

The population isn't really increasing to any extent. There's actually indication that calving rates are dropping.

· Joshua SmithSmith explained what the long-term survey data suggest about population growth and reproduction.

Long-term records suggest the population is stagnating and that calving rates may be falling. Breeding cycles once thought to restart every three to four years are now stretching toward five years. Smith said researchers need a decade and several returns by reproductive females to understand the population’s direction, making the 50-year record essential for interpreting the fluctuations.

The three-year cycle that we used to always pride ourselves on is extending.

· Joshua SmithSmith described the lengthening interval between whale births.
About this summary

Originally published by ABC Australia in English. Translated, summarized, and contextualized automatically by DistantNews, with a note on how the source frames the story. Not individually reviewed before publishing. How this works.

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