Beaked whales have rarely been seen. Now scientists are using underwater sounds to help identify these mysterious creatures.
On a bright, almost windless day in early June 2024, scientist Elizabeth Henderson was aboard a boat off the sun-drenched coast of Baja California. She and her team perched halfway up the vessel’s mast, wielding powerful binoculars and peering round at the calm water.
They were looking for beaked whales, a group of species that aren’t often sighted because they dive deeper and longer than any other mammal – with some known to dive nearly 2 miles (3km). Even when they surface, their relatively small, light grey bodies are hard to spot. “Depending on the light, they could just look like a wave,” Henderson says.
It was a few days into their expedition, and Henderson and her team had no luck. But then a cry came up from the boat below – it was the captain, whose eyes were on the water closer to the vessel. “There’s a whale next to us!” he exclaimed. It was actually a pair of juveniles, and they were swimming alongside the boat.
“One assumption about beaked whales that has always been made is that they don’t like boats,” says Henderson, a bioacoustic scientist at the US Navy Marine Mammal Programme where she studies the vocalisations and behaviour of marine mammals. “But they were not boat-shy at all. They were curious about us.”
Little is known about beaked whales. Currently 24 species are known to science, thought to make up around 25% of all whale and dolphin species. Some species have never been seen alive, and are only known about because their bodies have washed up on the shore. But new ways of listening to them, and more studies that are capturing their distinctive underwater clicks and squeaks, are slowly revealing the secrets of the world’s most elusive whales.
Henderson’s sighting came as a surprise in more ways than one. Based on sound alone, the team weren’t expecting to come across this beaked whale species. They had heard the BW43 pulse (BW for “beaked whale”, with a peak frequency of 43kHz), thought likely to be associated with the endangered Perrin’s beaked whale. But they took a biopsy, and the lab results would later reveal that this was another species: the gingko-toothed beaked whale, named after the distinctive gingko-leafed shape of its teeth.
“It was amazing, it was so unexpected – and for a species that has never been seen alive in the water, or in the wild. It’s a family of species that you assume you’re never going to see up close. To have them right next to us was the coolest thing ever,” says Henderson.
Beaked whales’ long, deep dives mean they’re difficult to study, explains Oliver Boisseau, senior research scientist at Marine Conservation Research, a UK non-profit. “Beaked whales have traditionally been overlooked,” he says. “They’re often offshore, they’re hard to access, and they’re cryptic, which means they’re hard to see.”
A new species, Ramari’s beaked whale, was discovered as recently as 2021. “It’s quite something in the 21st Century to still be discovering new mammal species that are the size of family cars. It’s quite mind-boggling,” Boisseau says.
Recent scientific interest has been prompted by mass strandings, thought to be caused by navy sonar. Scientists don’t understand the exact relationship between sonar and beaked whales, but one theory is that navy sonar prompts the mammals to surface too quickly, causing bubbles in their blood similar to when scuba divers suffer from “the bends”. “There’s sudden strong interest in this quite acute conservation challenge,” Boisseau says.
It is sound that is harming the whales – but it is also sound that is helping science understand them. “They rely primarily on their acoustics,” Boisseau says – they make and listen to sounds to help them forage, mate and navigate. “This is really how they interpret the world around them. So that’s an excellent window into their world below the water.” (BBC)
