50 years after whaling, behavioural effects linger

Fifty years after the end of whaling that decimated the humpback whale population in Oceania, the effects are still rippling through the animals’ behaviour.

A study of humpback whales in New Caledonia suggests changes to patterns in females’ selection of males for breeding.

“Whaling casts a very long shadow,” says Dr Emma Carroll of Waipapa Taumata Rau, University of Auckland, a co-author of the research in the scientific journal Current Biology.

“Even 50 years later, the effects are still working their way through the population.”

Studying 485 male humpbacks in New Caledonia between 2000 and 2018, researchers found signs that mate selection changes as the population becomes older and more numerous.

More breeding by younger males may have helped the whale population to maintain genetic diversity and avoid inbreeding after the Oceanic population declined to fewer than 200 in the 1970s – a so-called demographic bottleneck.

Now, females have increased their selection of older males.

To attract mates, male humpbacks sing some of the most complex song of the animal world and secure roles as females’ escorts, sometimes after aggressive competition with rivals.

“Virtually all populations of whales have changed due to whaling; our work shows that they continue to change as they recover,” said Dr Franca Eichenberger, the lead author of the study, from the University of St Andrews in Scotland. “This is why the continued long-term monitoring of previously exploited whale populations is so important.”

The study relied on epigenetic data from long-term monitoring in a breeding ground in New Caledonia by the NGO Opération Cétacés.

The work was primarily funded by the Royal Society of London and the National Geographic Society. Carroll was funded by New Zealand’s Royal Society Te Apārangi.