Smallest baleen whales right at home in Australian waters

Pygmy right whales remain in Australian waters throughout the year, foregoing the long-distance migrations of larger whales, according to new research by University of NSW scientists.

“They’re our little homebodies, just happy to hide away and never leave the comforts of our continental waters,” says marine ecologist and author Professor Tracey Rogers from UNSW.

Little is known about Pygmy right whales Caperea marginata – the smallest member of the filter-feeding baleen whales – because the species is rarely sighted and often mistaken for minke whale. 

The species grows to 6.5 metres long and weighs up to 3.5 tonnes, small for its species.

Researchers revealed the new information about the animal’s diet and movements by analysing chemical clues in the animal’s baleen plates, the long bristles that hang from the whale’s upper jaw allowing them to take in small food such as krill. 

Publishing in Frontiers in Marine Science, the researchers analysed chemical isotopes in the baleen plates of 14 pygmy right whales on loan from the South Australian Museum.

The specimens reflect whale’s living between 1980 to 2019. The plates came from 6 males, 6 females and 2 unknown individuals.

During each Pygmy right whale’s lifetime, in addition to taking in food, their baleen plates are collecting chemical information about the whale’s behaviour and movements in the form of isotopes of carbon and nitrogen.

Each plate, contains 3 to 4 years of data on the individual whale’s diet and movements, analysed using an organic elemental analyser and isotope ratio mass spectrometer. 

To find out where and what the whales ate, the information was then overlayed with data on the chemical isotopes and distribution of Australian and Antarctic krill species.

The analysis of these chemical clues revealing that unlike larger whale species, pygmy right whales tend to remain in Australian waters rather than migrating.

“Their isotopic record shows they remain in mid-latitude waters year-round off southern Australia, feeding on krill and copepods (small crustaceans),” lead author and marine ecologist Adelaide Dedden says. 

“There was no evidence of feeding in Antarctic waters at all, suggesting the waters off Southern Australia appear to be able to support their needs year-round.”

The findings can provide a basis for further research into the petite whale species.

“Now we have increased evidence they live in this mid-latitude distribution, it would be ideal if we could do some satellite tagging to more closely monitor their movements and see exactly where they’re travelling around in the region,” Dedden says.