Shhh! The orcas can’t hear their dinner

When an orca hunts salmon, it clicks and buzzes.

It sends a beam of sounds from its nasal passages into the murky depths in hopes that the sound waves will bounce back and reveal the location of its next nutritious meal.

Those hopes are often dashed when noise from passing vessels drowns out orcas’ sonar signals.

Underwater noise—whether from rumbling container ships, rattling ferries, chugging fishing boats, or whining speedboats—has long been understood to threaten the survival of the Northwest’s endangered orcas.

Some ships and ports in Washington and British Columbia have taken steps to reduce the din below, though increasing maritime traffic could negate those efforts.

A new study reveals how vessel noise masks orcas’ sonar at every stage of the hunt—from searching, to pursuing, to capturing prey.

“As noise is increasing, the orcas are actually spending more effort trying to find fish,” University of Washington whale researcher Jennifer Tennessen said. “These are animals that rely entirely on sound to locate and pursue and ultimately catch their prey.”

RELATED: Puget Sound tanker traffic thickens as Canadian pipeline boosts oil flow

In noisy conditions, orcas spent more time and energy scanning the sea for fish, the new study in the journal Global Change Biology found. When orcas did locate a potential meal despite the noise, they were less likely to successfully catch it.

Females were especially affected: They would often not bother to chase prey they had detected in noisy conditions—when the odds of a successful hunt are lower.

“Both males and females ultimately are less likely to catch fish as it gets louder,” Tennessen said.

Using sounds and data from recorders temporarily suction-cupped onto the backs of orcas in Washington and British Columbia, researchers were able to hear what whales hear as they hunt.

Getting even a brief glimpse into the hidden world of a hunting orca is no small feat.

After getting permits to closely approach this protected species, researchers headed out in small boats. Once an orca was nearby, a researcher stood on the bow with a 23-foot carbon-fiber pole. As a whale momentarily surfaced, the researcher aimed the far end of the pole to press an electronic tag onto the whale near its dorsal fin.

For a few hours, the tag’s two microphones captured the various sounds the orca heard and made, pressure and temperature sensors recorded water conditions, while its accelerometer captured the animal’s motions in 3-D detail.

Within 1 to 8 hours, the suction cups released, and the tag floated to the surface.

Researchers generally consider the implosion of Chinook and other salmon populations, not noise or other forms of pollution, to be the greatest threat to the survival of southern resident killer whales, an endangered population that numbers just 74 individuals.

RELATED: Bellingham man fined $1,000 for steering yacht through orca pod

Tennessen said restoring salmon habitat and boosting salmon populations is a long-term endeavor.

“We can't address that overnight,” she said. “It will take years for us to see the kinds of salmon returns that we need to see.”

Tennessen said, with noise at least, there’s a quick fix.

“One of the easiest ways to have an immediate impact on noise is just by slowing down vessels,” she said. “If we slow down ships—it's just physics—we know that sound reduces.”

RELATED: Electric ferries are cleaner and quieter. For orcas, that might not be enough

Ship noise is unregulated, but voluntary efforts on both sides of the 125-mile maritime border between Washington and British Columbia have muffled some of the din.

In 2023, 87% of ships slowed down during Canada’s June-November voluntary slowdown in Haro Strait and Boundary Pass, west and north of the San Juan Islands, according to the Vancouver Fraser Port Authority. During an October-January voluntary slowdown in U.S. waters, 71% of big ships participated, according to the nonprofit Washington Maritime Blue.

Biologist Michael Weiss with the Center for Whale Research, who was not involved in the new study, said it shows that efforts to reduce the number and speed of vessels in the Salish Sea could improve the endangered orcas’ ability to find salmon to eat.

“On the flip side, it suggests that projects like the Roberts Bank Terminal 2 expansion [in Delta, British Columbia, less than a mile north of the U.S. border] that are likely to increase large vessel traffic could have major negative consequences for the southern residents,” Weiss said by email.

The May 2024 expansion of the Trans Mountain Pipeline from Alberta to Burnaby, British Columbia, has led to an increase in tanker traffic in orca habitat on both sides of the international border.

Starting in January, all boats will be required to stay at least 1,000 feet away from any endangered orcas in Washington waters.

“Circumstances are changing almost as quickly as the science can keep up with,” biologist Rob Williams with Oceans Initiative, who was not involved in the study, said by email. “In the decade since these data were collected, the [southern resident killer whale] population has declined and become even more inbred.”

The researchers tagged 34 northern resident killer whales and 23 southern residents with suction cups from 2009 to 2013.

Southern resident killer whales, so named because their home waters include the southern half of Canada's Vancouver Island, have been on the U.S. endangered-species list since 2005, when they numbered 87 individuals, 13 more than today.

RELATED: Endangered baby orca J60 missing, presumed dead

Northern residents are a large and growing population of fish-eating orcas that roam from the northern half of Vancouver Island to Southeast Alaska. Canadian officials estimated the northern residents’ population at 342 whales in 2022, an increase of 69 animals in a decade.

Tennessen said the new paper builds on earlier studies of the tag data that worked out which sounds orcas make during various stages of a hunt and how to quantify vessel noise.

She said the work was also delayed by funding difficulties, the Covid-19 pandemic, maternity leaves, and the need to collaborate internationally with Canadian researchers.

“I absolutely wish we could go from data collection to rapid dissemination — certainly the whales would benefit from this,” Tennessen said by email. “But the unfortunate reality is that science takes time and money, and both of these are often limited.”