Keywords: Mammals, Salish Sea Currents magazine, Killer whales, Species of concern, Noise

Just last year, scientists published the first direct evidence that noise interferes with orca feeding behavior. Officials hope a new law establishing a larger buffer zone between boats and endangered southern resident orcas will mean quieter seas and healthier whales. 


On January 1, 2025, a new law went into effect in Washington: in state waters, all boaters must stay at least 1,000 yards from any southern resident killer whale that happens to be in the vicinity. If a southern resident approaches a boat within 400 yards, that boat must shut off its engine, luff its sails, or, if a kayak or canoe, stop paddling until the killer whale leaves.

“Vessel noise is one of the three key threats to the Southern Residents, along with toxic contamination, and a lack of prey,” Dr. Julie Watson, killer whale policy lead with the Washington Department of Fish and Wildlife (WDFW), said in a press release. “WDFW and partners are working to address these threats, and this new 1,000-yard buffer is a major step in reducing the impacts of vessel disturbance on SRKW behavior. Boaters reducing noise by staying farther away effectively makes more prey available to SRKW by making it easier for the whales to find and catch salmon.”

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Southern resident killer whale distance requirements for boats in Washington State and Canadian waters. Graphic: BeWhaleWise.org

Federally listed as endangered since 2005, the southern resident population currently numbers 73, down from a high of 97 in the late 1990s, and far below the historical high of at least 200 individuals prior to the capture era, when dozens of killer whales were rounded up and sent to aquaria all over the world. As their plight has worsened, the southern residents have only become more popular, to the point that they are now regional celebrities, beloved of resident watchers in the United States and Canada and beyond.

One of the ways to see the southern residents on those increasingly rare occasions when they are in the Salish Sea is on a whale watch tour. The industry is robust. At present, the Pacific Whale Watch Association has thirty members in Washington and British Columbia; of those, seventeen have a killer whale in their logo. On everything from larger motorized vessels to rigid-hull inflatables, from sailboats to kayaks, those companies take about 400,000 people out to the Salish Sea to try to catch a glimpse of the southern residents or, increasingly, the mammal-eating transients. Over and above their attentions is a perpetual increase in commercial shipping traffic. Per the most recent estimate from the Friends of the San Juans, an advocacy group, the number of vessel trips through the Strait of Juan de Fuca numbered more than 11,000.

A collage of images of orcas with different types of boats. The main image (left) is of two orcas swimming together in the foreground with a tanker in the distance, a smaller images (upper right) depicts a single orca swimming alongside a yellow kayak and

Noise from boats of all kinds affect southern resident killer whales. The louder the environment, the more time orcas spend searching for food at all depths and the more likely they are to miss fish they are hunting. Females are less likely to bother chasing fish at all. Photos: (Left) AdobeStock; (upper right) Andrew Redding (CC BY-NC-ND 2.0); (lower right) AdobeStock.

This question of how and why boats and the sounds they make can affect killer whale foraging was the subject of a recent paper in Global Change Biology by Jennifer Tennessen, a biologist at the University of Washington. That underwater sound has an effect on killer whales is taken as a given, but until now most of those effects have been inferred. “Before, we didn’t have a good understanding of how noise actually affects the ways killer whales are trying to find pursue and capture their food,” Tennessen says. Oh, scientists and managers have a lot of models for how sound should interact with killer whales, and have shown—theoretically—that noise ought to interfere with their foraging efforts. But due to various logistical challenges and limitations based on how people observe whales, how they measure sound, and so on, it has been hard to figure out empirically how and to what extent noise can interfere with foraging.

“All noise matters to the whales. If we can make their habitat a little quieter, then the natural outcome of that would be being able to catch more fish." ––Jennifer Tennessen, University of Washington biologist.

In the paper, Tennessen and her colleagues from Canada and the U.S. used several years’ worth of tracking data to look at the relative fortunes of the southern residents and the northern resident killer whales, another distinct group that exhibits similar life history characteristics—salmon-loving, tight family groups, and so on—save for the fact that they make their living in the quieter inland waters around northern Vancouver Island. The data came from an instrument called a DTag. A biologger about the size of a mango, a DTag is affixed to an orca’s back via suction cups. The tag then records a trove of data—sounds the orca hears and the orca makes, how deep the animal dives, how it moves in three dimensions when it chases its prey—before popping off after, at most, about a day, and floating to the surface, where researchers can collect them. “With the DTag, we can know how loud it is at the location of the whale,” Tennessen says. “Not two kilometers away, not on the hydrophone mounted on the bottom, but on the hydrophone on the whale’s back, about a meter from whale’s head.”

A killer whale with a digital acoustic recording tag on its back swimming in Puget Sound

A digital acoustic recording tag, or DTag, is attached temporarily to an orca swimming in Puget Sound. Photo: NOAA/NWFSC (taken under NOAA research permit No.781-1824 and 16163).

Tennessen looked at a range of foraging behaviors across a range of orca diving depths. Given the noise levels they were experiencing, how frequently were the orcas searching for fish? How frequently did they chase fish? How frequently did they catch fish? And how frequently did these patterns vary based on the depth to which the killer whales were diving? Tennessen found that the louder the environment, the more time orcas had to spend searching for food at all depths. They were also much more likely to miss the fish they were chasing. Finally, and perhaps most notably, there were effects specific to an orca’s sex: when noise levels increased, it was females that were less likely to bother chasing fish at all in the first place.

Earlier research had shown an effect of vessel proximity on orca foraging. Indeed, it was a paper published in 2021 by Marla Holt, a biologist with the National Oceanic and Atmospheric Administration (NOAA), that found a profound effect of vessel proximity on orca behavior: when boats were within 400 yards, females would often stop feeding altogether. But it was hard to know what exactly of that nearness affected the whales. Merely the physical presence of the boats? Their sound? Some combination of the two? Tennessen’s paper is the first to show direct impacts of noise. So while the state regulations may be based more on the 2021 paper, Tennessen notes that getting boats to take a step back likely will have many benefits. “All noise matters to the whales,” she says. “If we can make their habitat a little quieter, then the natural outcome of that would be being able to catch more fish. The new regulations may not reduce any one particular ship’s noise, but they should collectively reduce the amount of noise the southern residents encounter, and we’re hopeful that will help them.”

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A killer whale with a digital acoustic recording tag swimming in Puget Sound . Photo: NOAA/NWFSC (taken under NOAA research permit No.781-1824 and 16163).

Research on the sounds and feeding behavior of Puget Sound's southern resident orcas is providing new insight into how the whales respond to underwater noise. A recent online conference brought together some of these findings along with discussions on how to reduce the impacts of noise from vessel traffic.


About the author: Eric Wagner is a staff writer with the Puget Sound Institute. He has a Ph.D. in Biology from the University of Washington and is the author of Once and Future River: Reclaiming the Duwamish, Penguins in the Desert, and After the Blast: The Ecological Recovery of Mount St. Helens. His essays and journalism have appeared in The Atlantic, High Country News, Orion, and Smithsonian, among other places.

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