Puget Sound orca whales have to raise their voices to be heard about the racket of underwater vessel noise, researchers have found

Orca whales are raising their voices to be heard above the noise of vessel traffic, researchers have learned.

Scientists already knew the orcas make longer calls to compete with background noise. But this is the first evidence that the southern-resident population of orcas that frequents Puget Sound is also making louder calls.

The findings were published in the January issue of the Journal of the Acoustical Society of America and already have had an impact. Policy makers at the federal fisheries service consulted an early version of the manuscript as they shaped new regulations proposed to protect endangered southern-resident orca whales, including restrictions on whale-watching vessels.

The regulations, which could be proposed as soon as this summer, may restrict how closely boats may approach orcas, to reduce the underwater noise the animals must contend with.

Sound is important to the J, K, and L pods of southern residents, who use calls to communicate with each other, stick together, find food, and possibly, share their catch.

The question is what the orcas will do if their world continues to get noisier — and how noise is already affecting them.

“This shows they are able to compensate to a degree,” said lead author of the paper, Marla Holt. “The question is: What are the consequences? If it’s even louder, what will happen? Do they reach a point where they can’t raise their voices any more?”

Scientists also want to know whether the whales are stressed by having to raise their voices. And they wonder if the noise makes it harder to forage.

Jenny Atkinson, executive director of the Whale Museum in Friday Harbor, said people are making it tougher on an already endangered animal population.

Seven members of the southern-resident population disappeared this year and are presumed dead.

“Where we play is where they live,” Atkinson said. “We ought to be doing everything we can do to help this population recover.”