24 February 2023
A new study suggests the singing noises made by humpback whales might be a sign of loneliness.
Scientists who recorded humpback whale behavior in Australia discovered that fewer whales made the singing noises, also called wailing, as their population grew.
"Humpback whale song is loud and travels far in the ocean," said marine biologist Rebecca Dunlop of the University of Queensland in Brisbane. She has long studied humpback whales and helped lead the new study. Her work has centered on humpbacks that reproduce near Australia's Great Barrier Reef.
Dunlop told The Associated Press she made an unexpected find as whale numbers sharply rose following the end of commercial whaling. "It was getting more difficult to actually find singers," she said.
Dunlop added, "When there were fewer of them, there was a lot of singing – now that there are lots of them, no need to be singing so much."
Scientists first began to hear and study the complex songs of the humpback whales in the 1970s. They used underwater microphones to do so. Only male whales sing. Scientists think the whales sing to seek mates or show power.
Eastern Australia's humpback whales came close to disappearing in the 1960s, when their number dropped to around 200. But over time the population began to regrow, climbing to about 27,000 whales by 2015. That number is near estimated pre-whaling levels.
As the density of whales increased, their singing behaviors changed. While 2 in 10 males made wailing noises in 2004, 10 years later the number had dropped to 1 in 10, Dunlop said. The team's study appeared in a recent issue of Nature Communications Biology.
Dunlop said she thinks singing played a big part in bringing in mates when populations were severely reduced. "It was hard just to find other whales in the area, because there weren't many," she added.
When humpbacks live in denser populations, males looking for mates also have to deal with competing whales. Dunlop explained the singing noises might bring in other possible mates.
Boris Worm is an ocean biologist at Canada's Dalhousie University. He was not involved in the research. "As animal populations recover, they change their behavior – they have different constraints," Worm said.
The research suggests the seas are still noisy with humpback whale sounds. Many humpbacks seek to bring in mates with a combination of singing and physical movements, the study notes.
The large increase in the humpback population during the study period provided valuable data about changes in the animals' behavior, said Simon Ingram. He studies humpback whales at the University of Plymouth in Britain.
Ingram said humpback whales must have been singers long before whaling reduced their numbers. But the new study demonstrates how necessary their complex and beautiful songs were to their survival and recovery, he added.
"Clearly singing became incredibly valuable when their numbers were very low," Ingram said.
I'm Bryan Lynn.
The Associated Press reported this story. Bryan Lynn adapted the report for VOA Learning English.
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commercial – adj. related to business or the part of a business or service aimed at making a profit
constraint – n. something that limits what a person can do