Fin Whales are the second largest animals in the world and yet the least understood. But scientists are now trying out ways to find out more about these sea mammals by using technology used to study earthquakes.
Fin whales are usually called the ‘greyhounds of the sea’ with all the world oceans being their playground. Because of their global range, the whales make it hard for scientists to study them closely.
The animals though, are at risk from vessel hits and this was made more apparent by the carcass of a whale that washed in the Seattle beach area.
In order to learn more about their swimming behaviour, which could help vessels avoid the animals and also understand where and what they ate, University of Washington oceanographers are using seafloor seismometers, devices that record vibrations.
A series of three papers published this winter in the Journal of the Acoustical Society of America notes that whale calls can be easily interpreted from the earthquake sensor data. It is a simple, easily accessible source and can help monitor whales.
The studies are also the first to match whale calls with fine-scale swimming behavior, providing new hints at the animals’ movement and communication patterns.
The research began a decade ago as a project to monitor tremors on the Juan de Fuca Ridge, a seismically active zone more than a mile deep off the Washington coast. During the research, the team collected an entire year’s worth of seismic data.
“Over the winter months we recorded a lot of earthquakes, but we also had an awful lot of fin-whale calls,” said principal investigator William Wilcock, a UW professor of oceanography. At first the fin whale calls, which at 17 to 35 vibrations per second overlap with the seismic data, “were kind of just a nuisance,” he said.
But in 2008 the previously discarded whale calls were studied again after the scientist received funding from the Office of Naval Research.
Dax Soule, a UW doctoral student in oceanography, compared the calls recorded by eight different seismometers. This had been done previously for two or three animals but during the current study they observed and analyzed more than 300,000 whale calls.
According to Science Daily, the method is similar to how a smartphone’s GPS measures a person’s location by comparing paths to different satellites. Researchers looked at the fin whale’s call at the eight seismometers to calculate a position. That technique let them follow the animal’s path through the instrument grid and within 10 miles of its boundaries.
The inexpensive technique gave the scientists a wealth of information.
Soule created 154 individual fin whale paths and discovered three categories of vocalizing whales that swam south in winter and early spring of 2003.
He also found a category of rogue whales that traveled north in the early fall, moving faster than the other groups while emitting a slightly higher-pitched call.
“One idea is that these are juvenile males that don’t have any reason to head south for the breeding season,” Soule said. “We can’t say for sure because so little is known about fin whales. To give you an idea, people don’t even know how or why they make their sound.”
The researcher says that because the second-long chirp emitted by the whale roughly every 25 seconds is consistently loud and at the lower threshold of human hearing, it is within range of earthquake monitoring instruments. These loud, repetitive bleeps are ideally suited for computer analysis.
Michelle Weirathmueller, a UW doctoral student in oceanography determined the loudness of the call from the data. She found the fin whale’s call is surprisingly consistent at 190 decibels, which translates to 130 decibels in air — about as loud as a jet engine.
“We’d like to know where the fin whales are at any given time and how their presence might be linked to food availability, ocean conditions and seafloor geology,” Weirathmueller said. “This is an incredibly rich dataset that can start to pull together the information we need to link the fin whales with their deep-ocean environments.”
The research opens a wide area of study for scientists around the world as an additional use of the already collected seismic data.