The legendary humpback whales along the east coast of Australia just don’t sing as much as they used to.
Two researchers at the University of Queensland (UQ) found that males went from singing to attract a mate to physically competing with other males within 18 years.
“In 1997, a singing male whale was almost twice as likely to attempt to mate with a female as a non-singing male,” said UQ animal physiologist Rebecca Dunlop.
“But by 2015 it had reversed, with non-singing males being almost five times more likely to be caught in breeding attempts than singing males.”
Men are thought to sing their soulful songs in part to attract mates, and traditionally those without songs were less likely to find a wife.
But what made the switch from singing to fighting? Well, for that you have to go back to our history of whaling.
Before whaling, there were approximately 26,000 East Australian humpback whales (Megaptera novaeangliae) living in the Southern Ocean.
But by the 1960s there were only about 200 left – we had hunted them almost entirely to extinction.
Once whaling ceased, the numbers recovered. By 1997—when this study began, there were 3,700 whales and by 2015 there were 27,000 whales—back to pre-whaling levels. The researchers also had data from 2004 and 2008 in their dataset recorded near Noosa in Queensland.
This rebound is obviously a fabulous track record. However, with more males, more problems arise.
“When the competition is fierce, the last thing the male wants to do is advertise that there is a female in the area because he might attract other males who might outcompete the singer for the female,” Dunlop said .
“By switching to non-singing behavior, the males may attract less competition and be more likely to retain the females.”
This shows a kind of “social evolution” happening in real time as the population grows.
“It’s a pretty big change in behavior, so humans aren’t the only ones undergoing big social changes when it comes to mating rituals,” says Dunlop.
“In humpback whales, physical aggression usually manifests itself as ramming, charging, and trying to headbutt each other.
“This carries the risk of physical injury, so men must weigh the costs and benefits of each tactic.”
The research was published in communication biology.