Keywords: Mammals, Marine habitat, Monitoring

The Salish Sea may be a giant ‘practice room’ for humpback whales as they get ready to sing in their winter breeding grounds in Hawaii and Mexico. A network of hydrophones is recording it all.

The sound came at dusk about a half hour after sunset. The hydrophone at Point Robinson captured a series of descending moans from a giant beast making its way through the murky waters of Puget Sound. Through the hum of the recording came the classic sounds of a humpback whale.

To scientists, the call was an announcement of sorts, the equivalent of a resounding “we’re here.” It marked one of the first humpback vocalizations ever captured in south Puget Sound, and it was part of an upward trend for humpbacks in the Pacific Northwest in general.

Once hunted to near extinction, the whales are now making what many are calling a “humpback comeback.” Last year was a record-breaker for the whales with about 2000 individuals documented inside the waters of Washington and Southern British Columbia. That is up from just a handful of sightings in the 1980s and 1990s, and, as with the old adage about smoke and fire, where there are whales, there are sounds.

During the fall months, the Salish Sea comes alive with “whups,” “moans,” “growls” and an assorted variety of “creaks,” “trumpets,” “buzzes” and other humpback vocalizations. These calls and many others are being carefully collected by scientists in a new repertoire catalogue sponsored by the Orcasound hydrophone network.

While not necessarily songs themselves, the sounds are a prelude of sorts to what the whales will be singing later in the year on their breeding grounds in places like Hawaii and Mexico. In the coming winter, in clear, tropical waters around the world, male humpbacks will sing day and night, turning the ocean into a vast concert hall.

Famous singers

Humpbacks are famous for their calls. If any whale were to win a Grammy award, it would probably be a humpback. Thanks in part to popular record albums from the 1970s, the whales’ low, cello-like songs have become synonymous with the music of the deep. But like most good musicians, the whales didn’t get here without a lot of practice.

Studies show that the whales pass their songs to each other from year to year, gradually learning and refining them, stringing together different melodies and song ‘bouts.’ Here in the Salish Sea, humpbacks began testing out their voices this month.

Underwater view of one humpback whale and the tail of another.

Humpback whales in the singing position. Photo: Louis M. Herman/NOAA (CC BY 2.0)

“The whales are actually present in Haro Strait as soon as June, but they don’t start vocalizing usually until late August or early September,” says marine mammal biologist Emily Vierling, one of the creators of the catalogue. “So they’re basically silent until those periods.”

Vierling and her collaborators Scott and Val Veirs at Orcasound started collecting these fall sounds as a way to document humpback behavior and to create a baseline to measure changes over time. One of their concerns was how the sounds of large vessels moving through busy Haro Strait might affect humpback vocalizations and activity.

 “Obviously, the Haro Strait between Seattle and Victoria is used regularly for massive shipping vessels,” Vierling says, “and a lot of their motors operate at the same frequency that humpback whales use to create their vocalizations. It will be interesting to see if their repertoires change, or if they shift frequencies to better [communicate].”

The database, which was inspired by Vierling’s earlier experiences at the Canadian hydrophone network OrcaLab, is also grist for behavioral studies, including speculation about how and when humpbacks develop their famous breeding songs. Vierling has noticed that the whales in the Salish Sea occasionally put some of their non-song vocalizations together in intriguing ways. Could these vocalizations be early drafts of future songs?

“We can maybe phrase it as like a warming up, or a short performance,” Vierling says. “But we really don't know the context of why these are being produced early on. It may be a practice round. It could be that they are having certain social interactions, and that's why they're being produced. It's very open ended.”

The next step, Vierling says, is to compare the Salish Sea recordings with recordings of finished songs captured in the humpback breeding grounds. If the songs match, according to Vierling, it could be evidence that the whales begin practicing earlier than previously thought for their big tropical performances.

For those who might want to hear the whales tune up this fall, Orcasound will be streaming audio from Haro Strait continuously on its website. A.I. will soon be listening too. Sounds from the catalogue are being fed into algorithms that will one day help scientists sort through huge amounts of audio data. The HALLO (Humans and ALgorithms Listening for Orcas) annotation team from Simon Fraser University in collaboration with Orcasound is developing automatic detection software “in the hope that we can one day produce a simpler way to evaluate these calls,” says Vierling.

About the author: Jeff Rice is the managing editor of the Encyclopedia of Puget Sound.

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