Baby humpback whales ‘whisper’ or speak in incredibly faint squeaks and grunts to their mothers as they don’t want any unwanted listeners, researchers discover in a new study.

A team of Australian and Danish researchers tracked 8 baby humpback whales and two mother whales for around seventy hours, and were surprised to learn about the baby whales’ quiet grunts and squeaks.

The researchers estimated that the baby whales whisper to their mothers to avoid unwanted listeners or potential predators, such as killer whales that can kill and eat these calves.

Simone Videsen of Denmark’s Aarhus University said, “There are lots of killer whales in the area which are predating on these calves, and they can use these sounds between mother and calf as like homing cues.”

The researchers recorded the whispers made by the infant whales to their mothers using devices attached to their bodies.

The international team of researchers reported their findings in the latest issue of the journal Functional Ecology.