Baby humpback whales face something of a baptism of fire when they're introduced to the world. Born in the tropics during the summer, these calves take on as much weight as possible before embarking on an epic 5,000-mi (8,000 km) journey to the food-rich waters of the Antarctic or Arctic. Scientists know little about the calves' behavior during this long migration, but new recordings appear to have unearthed a crafty survival technique where they whisper to their mother to avoid detection by predators.

Adult humpback whale songs are famous for their complexity, duration and beauty, and it appears these creatures have a knack for nuanced acoustic communication from the outset. Looking to learn more about their vocal activity during their maiden voyage to the pole, scientists from Australia's Murdoch University and Denmark's Aarhus University tagged eight calves and two mothers in Australia's Exmouth Gulf prior to departure.

Attached to the whales via a suction cup, the tags captured sounds made and heard by the whales while also tracking their movements. This took place over 48 hours, before the devices detached themselves and floated to the surface.

The team found that the newborn whales communicated with their mothers through soft grunts and squeaks (which you can listen to here), and that these typically occurred while the whales were swimming. The researchers believe that this is a tactic employed to keep mother and child together while avoiding detection by killer whales, which like to chow down on baby humpbacks in the area, as well as by male humpbacks.

"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," says study lead author Simone Videsen.

The team says its findings also indicate that calves and their mothers may be sensitive to noise from ships, in the sense that louder ships could drown out their careful whispers. It says discovering more about their behavior during those crucial formative years will help inform conservation efforts going forward.

"This migration is very demanding for young calves," says Videsen. "They travel 5,000 miles across open water in rough seas and with strong winds. Knowing more about their suckling will help us understand what could disrupt this critical behavior, so we can target conservation efforts more effectively."

The research was published in the journal Functional Ecology.