Whispering baby whales.

Science Daily listens close to baby humpback whales whispering to their mothers:

Ecologists from Denmark and Australia used temporary tags on humpback mothers and their calves in Exmouth Gulf off western Australia to learn more about the first months of a humpback’s life.

According to lead author Simone Videsen of the University of Aarhus: “We know next to nothing about the early life stages of whales in the wild, but they are crucial for the calves’ survival during the long migration to their feeding grounds.”

Together with colleagues from Murdoch University, Videsen tagged eight calves and two mothers. To capture the faint sounds of the calves, they used special tags developed by the University of St Andrews.

The tags attach to whales via suction cups and record sounds made and heard by whales, along with their movements, for up to 48 hours before detaching to float at the surface.

The recordings also revealed that newborn humpbacks communicate with their mothers using intimate grunts and squeaks — a far cry from the loud, haunting song of the male humpback whale.

The data tags showed that these quiet calls usually occurred while whales were swimming, suggesting they help mother and calf keep together in the murky waters of Exmouth Gulf. “We also 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,” says Videsen.

Such quiet communication helps reduce the risk of being overheard by killer whales nearby, she believes: “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 findings will help conserve this important humpback habitat and — crucially — ensure these nursery waters are kept as quiet as possible.