Dr Emmanuelle Leroy of the University of New South Wales, Sydney, analyzed data from nuclear bomb detectors for her work as a bioacoustician – people who study the relationship between animals and the sounds they make and hear – when she noticed “an unusually strong signal” occurring in a strange pattern.
“At first I noticed a lot of horizontal lines on the spectrogram,” Leroy said in a statement. “These lines at particular frequencies reflect a strong signal, so there was a lot of energy there.”
She tried to solve the mysterious discovery by examining nearly two decades of underwater microphone data, available through the Comprehensive Nuclear-Test-Ban Treaty Organization, which uses advanced microphones on the ocean floor to detect possible nuclear bomb tests and prevent the development of more powerful explosives. Leroy studied frequencies, tempos, and structures to look for larger patterns that could reveal the source.
It proves the “songs” were from a seemingly elusive new group of pygmy blue whales – one of the world’s largest animals – never before seen in the middle of the Indian Ocean where their songs were detected.
Beast vocalizations have also been detected “as far north as the Sri Lankan coast and as far east of the Indian Ocean as the Kimberley coast in northern Western Australia”, Tracey Rogers, marine ecologist at UNSW and lead author of the whale study, said in the statement.
“Thousands of these songs were produced each year. They were an important part of the acoustic ocean soundscape, ”said Leroy, lead author of the study and former postdoctoral researcher at the university. “The songs couldn’t come from a few whales, they had to come from an entire population. “
The researchers compared the acoustic song compositions with those of three other types of blue whale songs heard in the Indian Ocean, as well as four types of Omura whale melodies in the same region.
Evidence shows that the music did not belong to any other whale in the Aquatic Quarter, suggesting that the group it came from is a new group that has managed to remain invisible, although the species is around two standard busses tall.
Although the discovery has yet to be confirmed by visual observations, which the researchers say can “be tricky and expensive to fund,” it is a victory for marine conservation.
Blue whales almost disappeared after the whaling boom in the 20th century and were unable to increase their numbers unlike other whale species in the southern hemisphere. Researchers estimate that less than 0.15% of blue whales in this region have survived whaling.
The new population, named “Chagos” after the group of islands near which their songs were detected, would only be the fifth group of pygmy blue whales in the Indian Ocean if confirmed, according to the published study. in April in the journal Scientific Reports.
“Southern hemisphere blue whales are difficult to study because they live offshore and don’t jump – they’re not show ponies like humpback whales,” Rogers said. “Without these audio recordings, we would have no idea that there was this huge population of blue whales in the middle of the equatorial Indian Ocean.”
Blue whale songs are like human slang
Blue whale songs can travel between 125 and 310 miles underwater, but they are mostly inaudible to human ears. Unlike humpback whales, for example, which are “like jazz singers” who change songs all the time, blue whales like more structure, Rogers said.
Even so, different populations of blue whales are known to vary their tunes from time to time, “similar to generational slang between humans,” according to the UNSW statement.
Additionally, these songs can educate scientists about animal population, spatial distribution, and migration patterns.
“We still don’t know if they were born with their songs or if they learned it,” Rogers said. “But it’s fascinating that in the Indian Ocean animals cross paths all the time, but whales from different regions still retain their distinctive songs.
“Their songs are like a fingerprint that allows us to follow them as they travel thousands of miles. “