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Whale skin sheds light on changed foraging habits

Analysis of chemicals in the skin of southern right whales has revealed their foraging habits have shifted in recent decades, likely in response to climate change.

Scientists from 36 countries, including Australia and New Zealand, measured the amounts of carbon and nitrogen isotopes in 1002 skin samples taken between 1994 and 2020.

Concentrations of the isotopes vary in different waters and show up in the skin of animals.

It takes up to six months for the isotopes to show in a whale's skin, allowing scientists to pinpoint where the mammals were six months earlier.

"Despite their large size, whales can be very hard to track," co-author and marine scientist at Macquarie University, professor Robert Harcourt, said.

"Using this technique, we have been able to piece together a map of where the southern right whales have travelled across the Southern Ocean."

Researchers also looked at data of more than 2600 whale-catches from 1792 to 1968, which suggested the species' historical foraging grounds were largely stable in mid-latitudes.

They compared this to the recent map, determining the southern right whale's foraging spots had shifted in the last 30 years reflecting the changing distribution of their prey.

Whales in the South Atlantic Ocean and southwest Indian Oceans travelled to Antarctic waters less often, probably because there was less krill there, researchers suggests.

In the southwest Pacific, whales still went south at certain times of the year, suggesting krill are still plentiful in that ocean.

"These results suggest that climate change has driven recent shifts in the distribution of southern right whales," Professor Harcourt said.

"This could help prioritise areas where conservation efforts should be focused."

The research was published this week in academic journal Proceedings of the National Academy of Sciences.