Baby humpback whales and their mothers communicate in "whispers" to avoid predators, a study has found.
When a mother whale and her calf call to each other, they use lower voices than if they were speaking to other adult whales, according to a study published by Functional Ecology in April.
Humpback whales use sound conduction in the water to communicate vocally with each other over long distances. Scientists wanted to gain a better understanding of how mother whales and their children communicate during the period where the whales are nursing, so they used suction-cupped sensors to study eight youngsters and two moms in Australia's Exmouth Gulf.
A mother humpback whale and her calf rest at the surface of the Caribbean Sea.
What they found was that the mother whales emitted low squeaks and grunts that could only be heard from about 100 metres away, while other whale calls could be heard from kilometres in the distance.
Killer whales often flock to the gulf in the hopes of separating young calves from their mothers before the whales migrate to their breeding grounds.
"This quiet communication may reduce the risk of predation from killer whales and harassment by male humpback whales," the study reads.
But human activity could disrupt the whales' clever communication method. The study found that noise pollution from ships near whale breeding grounds can obstruct their calls and lead to the pairs being separated. If a calf is separated from its mother while it is still nursing, it will likely die.
“We don’t know exactly what would happen in the case of a separation or whether they are able to compensate by producing louder signals,” lead author Simone Videsen told the Natural Resources Defense Council.
“However, if they do resort to louder calls, then that could potentially make them more detectable to predators.”
A 2016 study from the Royal Society found increased shipping noise in the North Atlantic was disrupting whale's foraging behaviour.
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