Seeing with Sound: Acoustic monitoring of beaked whales can help determine oil spill impacts

A beaked whale at the ocean's surface

A Gervais' beaked whale comes up to the surface to take a quick breath.
Credit: NOAA

By L.K. Ward and Danielle Hall

When compared to dolphins and large baleen whales, beaked whales lose a bit of the limelight. Their similarity to dolphins may create some of the confusion, but another reason why they seem so obscure is that their preferred swimming grounds are far offshore. Even worse, these shy and ship-wary marine mammals only need a quick breath at the surface to spend the next 40 minutes underwater diving for squid and fish. Plus, the many different species of beaked whale (there are over 20) look frustratingly similar. How then can we understand more about these elusive creatures?

The answer may be with sound.

In part through a study funded by the Gulf of Mexico Research Initiative, a group of researchers from the Scripps Whale Acoustics Lab, the Centre for Research into Ecological and Environmental Modelling at St. Andrews University, and the Scripps Acoustic Ecology Lab have made significant progress developing methods that can answer questions about not only beaked whales, but other whales and dolphins that we can’t easily see from a ship on the sea’s surface. The researchers can estimate how many beaked whales of a specific species pass through a given area using acoustic monitoring tools, and they hope to learn even more about the behavior of these whales—specifically, when and how they feed.

“Trying to study life at 1,000 meters below the surface of the ocean renders you almost completely blind,” explains Kait Frasier, Assistant Project Scientist at the Scripps Whale Acoustics Lab. “One of the best tools we have to locate whales and dolphins in the Gulf is sound.”

The key to this project is echolocation. Just like dolphins, beaked whales send pulses of high-frequency sound through the water that work like a SONAR ping to find prey in the dark waters of the deep. Each species of beaked whale sends out a unique frequency that scientists can use like a fingerprint to estimate how many individuals of a specific species are in a given area.

Examples of whale and dolphin sounds:

Cuvier's Beaked Whale:
Sperm Whale:
Atlantic Spotted Dolphin:
Audio courtesy of Kait Frasier.

For many parts of the world, population numbers for beaked whales are questionable or sorely lacking. In the Gulf of Mexico, this became immediately apparent after the oil spill of 2010.

When the Deepwater Horizon blowout and subsequent oil spill happened in April of 2010 some of the first images and headlines (after the tragic human loss) were about the impact on marine mammals. These charismatic creatures have long captured the public’s hearts, and their oiled figures were easy to spot and photograph when they came to breathe at the water’s surface where oil slicks formed. But without basic numbers on how many beaked whales lived in the Gulf, researchers were powerless when it came to pinpointing exactly how the oil spill was affecting the whales.

Animals that die offshore or in deep waters may never wash onto beaches and may go unaccounted for. Because of this, the number of marine mammals impacted is likely more than reported. And what about marine mammal deaths three, five, or even twenty years after the spill? Chemicals in oil can cause illness, oil vapors can impact marine mammal breathing, and eating fish that have ingested oil can have health consequences, all of which are not immediate.

“It’s not like we hear zero whales at the sites that were impacted by the oil spill,” says Simone Bauman-Pickering, a researcher at the Scripps Acoustic Ecology Laboratory. “That would be obvious, seeing flourishing populations to nothing in two years. But that’s not the case.”

After the oil spill, the Scripps labs got straight to work using a suite of stationary acoustic instruments (what they call passive because they simply listen for any nearby underwater sound) to try and get some sense of how many beaked whales were in the Gulf. High-frequency acoustic recording packages, called HARPs, were deployed to the seafloor for a year or more. The team also used a hydrophone array, made up of a line of high-frequency microphones, that is towed from the back of the ship during research cruises for real-time monitoring and finding animals within range.

The results of the study show that there are four types of beaked whales in the Gulf of Mexico. The most prevalent were Gervais’ and Cuvier’s beaked whales with the occasional appearance of Blainville’s beaked whale and a fourth unidentified whale that the researchers think may look so similar to the others that it has been misidentified from visual studies as one of the other three. Sound, it appears, is more powerful than sight. Researchers on the team hope to use this information as part of a long-term project in the Gulf that looks at how whale populations change over time after an oil spill.

Being on the forefront of scientific discovery may be exciting, but it isn’t without setbacks. Many of the tools utilized in this research are being invented and optimized along the way. Frasier works alongside Principal Investigator John Hildebrand and an entire team who not only spend hours first deploying then collecting the sound recording instruments in potentially rough seas, but also build the instruments and process the data. “It definitely takes a village,” says Frasier. A village is likely the only way to tackle the lab’s target research area, a 450 by 15-mile (724 by 24 km) region, and their various methods of data collection result in 230,000 hours of recordings to sort through.

But despite the difficulties, Frasier finds the opportunity for exploration in one of the last poorly understood ecosystems too tantalizing to pass up.

“That just makes the journey more exciting!”

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The Ocean Portal receives support from the Gulf of Mexico Research Initiative (GoMRI) to develop and share stories about GoMRI and oil spill science. The Gulf of Mexico Research Initiative (GoMRI) is a 10-year independent research program established to study the effect, and the potential associated impact, of hydrocarbon releases on the environment and public health, as well as to develop improved spill mitigation, oil detection, characterization and remediation technologies.

For more information, visit http://gulfresearchinitiative.org