'Whispering' Keeps Humpbacks Safe from Killer Whales

Pablo Tucker
April 28, 2017

© Mother-calf pair in Exmouth Gulf.

Baby humpback whales "whisper" to their mothers, according to a paper published Tuesday in Functional Ecology.

"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", said Videsen. All baby whales need to swim with their mothers, traveling for thousands of miles during the annual migration to the water of Antarctica which are rich in food. Exactly what happens during that period is a mystery.

Dr. Videsen said that she and her team were surprised with this revelation because "humpback whales are really vocal normally". Researchers do not have the necessary technology and equipment to trace them all the time, following their evolution and behavior. The recorders used suction cups to stick the devices to the calves' skin.

The tags showed that quiet calls usually occurred when whales were swimming, suggesting they help the babies not to get lost in murky water. "It can stay there for about a day and then it falls off", Videsen says.

When the researchers retrieved the devices and played the audio, they heard for the first time baby babbling vastly different than the haunting, eerie sounds emitted by adult male humpbacks. Mother whale and calf pairs make for a vulnerable target in the open ocean, both for killer whales looking for a meal and male humpbacks hoping to mate with the female. Videsen, speaking to NPR, said that the recordings were "squeaky" and some of them were like "grunting sounds". The low decibel sounds help the babies to ward off the gaze of predators away who may overhear loud sounds.

So why do the calves say anything at all?

Newborn humpback whales "whisper" to their mothers that they are not heard orcas, the researchers found.

Missing some content? Care to comment? 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.

Humpbacks are slow to reproduce. Pregnancy lasts for around one year and calves - which are 5 metres at birth - stay with their mothers until they are one year old. While in tropical waters such as Exmouth Gulf, calves must gain as much weight as possible to embark on their first, epic migration.

There are two major humpback whale populations, one in the northern hemisphere and the other in the south.

Researchers hope that their work will aid efforts to minimize human impact on marine mammals, and keep their nurseries safe and quiet. Instead of using sounds, the calves simply rub against their mothers to signal that they are hungry.

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