People of Northwest Public Radio
Thu May 16, 2013
Underwater Earthquake Recordings Reveal Mysterious Whale Calls
The Blue whale is believed to be the largest animal ever to exist. But nobody remembers number two. Fin whales are the second largest animals on the planet, weighing in at around 80 tons. And they’re very mysterious creatures. Now scientists have gained better access to the giant whale’s secret lives – almost accidentally.
About a decade ago, a series of underwater devices were deployed 150 miles off the coast of Vancouver Island to monitor earthquake activity.
“They discovered very quickly that in addition to all the earthquakes they had recorded, they had an amazingly rich data set of fin whale calls, which they weren’t expecting to see," Dax Soule says.
Soule is a research assistant in the School of Oceanography at the University of Washington.
He’s part of a team of scientists that analyzed a year’s worth of underwater seismic recordings from the Juan de Fuca ridge. It’s a hot spot for underwater tectonic activity. Turns out it’s also a hot spot for endangered fin whales, and these giant whales sing at a similar frequency to the deep rumblings of earthquakes.
The team was able to filter out the whale calls from the earthquakes. Then they used those calls to map whale movements as they traveled past a series of underwater earthquake recording devices, called seismometers.
That will help scientists better understand how these mysterious animals communicate and migrate.
“If you think about trying to get meaningful data on something that can swim 25-30 knots and is 80 feet long and spends most of its time in the deep sea, that’s a pretty big challenge," Soule says.
Kate Stafford is a whale expert with the Applied Physics Lab at the University of Washington.
“What it shows us is that the Juan de Fuca ridge area, the area off of Northern Oregon and southern BC, is really important for these whales," Stafford says. "They’re not just migrating through. They seem to be spending a fair bit of time in this region.
Fin whale calls aren’t musical like the songs of humpacks and other whales. But Stafford says their low frequency pulses help them stay in contact when they’re migrating.
"So it’s very similar to what birds do when they’re migrating at night. I’m here. I’m here. I’m here."
Other whales can hear these pulses miles away, allowing them to stay in touch as they travel all around the world’s oceans. But Stafford says that might not always be the case.
“This 20 hertz pulse that they make. That is right in the same frequency band as a lot of commercial shipping, and ship noise has been increasing as we’re starting to transport more and more things across the Pacific and across the Atlantic," she says.
Stafford says shipping noise could make it harder for the whales to communicate with one another or detect dangers, like oncoming ships.
A fin whale washed up near Seattle in April. It is believed to have died after colliding with a ship.
Copyright 2013 KUOW