Just beneath the water's surface off Queensland's coast, humpback whales can be heard singing clearly to each other, as new research shows they are learning complex tunes from other regions.
About 40,000 humpback whales are on their annual migration along Australia's eastern coastline and, according to Lady Elliot Island reef guide Jacinta Shackleton, it is as easy as putting your head under water to hear them.
"You can actually hear their song right at the surface of the water, and as you get deeper, they get louder," she said.
Their songs change every year, and researchers at the University of Queensland, including study leader Jenny Allen, have found neighbouring whale populations are learning each other's distinct tunes.
"So, the song is learned from one population to another."
Transmitting culture through song
The study examined songs of male humpback whales from eastern Australia and New Caledonia between 2009 and 2015 to decipher how culture transmits between the populations.
Dr Allen said it showed the whales learnt quickly and with remarkable accuracy.
"What we found was that they don't have to make it dumbed down at all," she said.
It is still unknown how close the populations must be to learn songs from one another.
"Both populations have a shared migration route that goes past New Zealand on their way to Antarctica, which is their feeding ground."
Dr Allen said there were some places where the singing was easy to hear.
"When they get to their breeding grounds, which are around the Whitsundays area, that's where they'll be singing the most," she said.
Hervey Bay is also an important stop for mothers and calves on their return travels south.
"If you stick your head in the water at Hervey Bay, you have a good chance of hearing singing," Dr Allen said.
Whale-watching season begins
The peak whale watching season is from July to October.
Ms Shackleton said that was the best time to see and hear the giants of the deep.
"It's pretty incredible for scuba divers because it does get really loud when you're down there," she said.
Understanding why whales sing
Researchers still do not know why whales sing, but they believe it could be linked to mating and reproduction.
"Females will make sounds, but they don't sing … it's only the males that sing," Dr Allen said.
"What we don't know is sort of who it's aimed at.
Dr Allen said the research helped understand how these whale populations interacted and how to better protect them.
"The east Australia population is doing really well, but the New Caledonia population is still endangered," she said.
