|A Humpback whale (R) and her baby (L) off the coast of Colombia|
Newborn humpback whales and their mothers whisper to each other to avoid attracting predators, scientists claim.
Known for their loud songs, the new discovery shows the giants use quieter communication to reduce the chances of them being tracked down by killer whales and male humpbacks looking for an opportunity to mate.
Dr Simone Videsen, from the University of Aarhus in Denmark, who led the research in Exmouth Gulf, Western Australia, said: "We ... heard a lot of rubbing sounds, like two balloons being rubbed together, which we think was the calf nudging its mother when it wants to nurse.
"Killer whales hunt young humpback calves outside Exmouth Gulf, so by calling softly to its mother, the calf is less likely to be heard by killer whales, and avoid attracting male humpbacks who want to mate with the nursing females."
The study tagged eight humpback calves and two mothers with suction cup devices that recorded both their sounds and movements for up to 48 hours before detaching and floating to the surface.