Sound pollution

Noise from marine traffic is interfering with orca calls (Photo: BioLib.cz)

Whales, interrupted

How noise pollution from boats and sonar from ships hurt orcas

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Sound pollution drowns out orca calls in northern B.C. Volunteers and researchers at OrcaLab listen in to find out how shipping traffic affects echolocation. (Produced by Graham Slaughter, Filmed by Marianna Angotti.)

An oceanside log cabin surrounded by a 1,000-year-old forest is illuminated by the glow of a computer screen. Even though it’s 2 a.m., Georgie Gemmell is still sitting at the laptop, which rests on a desk cluttered with binoculars, audio cassettes and hand-drawn maps. As if in a trance, the 22-year-old closes her eyes and listens to static white noise, which an underwater microphone is broadcasting through a set of speakers above her head.

Suddenly, a high-pitched whistle jolts Gemmell into action — she fumbles for a pen and a small red notepad and starts furiously scribbling notes. The whistle twists into a long, fluid song, which is joined by a chorus of haunting voices. A smile spreads across Gemmell’s face: a pod of orcas is nearby. “They sound like thunder at night,” she says. “You can’t see them when they swim past, but you can hear them. It’s really magical.”

Gemmell is a summer volunteer at OrcaLab, a research facility on British Columbia’s Hanson Island that focuses on killer whale acoustics. Two ferry trips, one water taxi and 10 hours of driving northwest from Vancouver, near the northern end of Vancouver Island, OrcaLab operates a network of six hydrophones that continuously listen to the ocean to record orca vocalizations. The songs are streamed online at orcalive. net, but in recent summers, boat noise has drowned out the orcas.

Tourism is a $13 billion annual industry in British Columbia, and in summer, visitors migrate from the ski slopes to the sea. Local First Nations fishermen also hit the water in pursuit of salmon. “Sometimes, cruise ships come in clumps and all of Johnstone Strait [the waterway surrounding OrcaLab] reverberates with the sound of their propellers,” says cetologist and former neuroscientist Paul Spong, who founded OrcaLab in 1970 and remains its director. “It’s unbearable for us to listen to, but I can’t imagine what it’s like for the whales.”

In 2001, the killer whale (Orcinus orca) was put on Canada’s Species at Risk registry. To help boost its population, Fisheries and Oceans Canada (DFO) made the Johnstone Strait a “critical habitat” for the orca. Although the designation is, in part, intended to monitor the “degradation of the acoustic environment,” Spong says it hasn’t diverted ships.

Since the 1980s, Canadian marine biologists have been trying to figure out how sound pollution affects whales. To assess the impact of boat noise on killer whales, says John Ford — an adjunct professor in the University of British Columbia’s zoology department and an orca expert who has worked for DFO for 10 years — one must understand how different orca populations hunt.

Reseachers theorize that northern resident orcas, a threatened population of about 260 whales that lives in Johnstone Strait, are picky eaters; they feed on chinook, the largest species of salmon. It is believed that orcas use an acoustic tool called echolocation to hunt, emitting a staccato “click” into the water and waiting for the sound to bounce back off potential prey. In quiet water, orcas can detect a chinook up to 100 metres away in seconds. “The northern residents need really quiet conditions to detect the echoes bouncing back from the fish,” says Ford. “The constant boat noise could interfere with their foraging efficiency by masking the sound of their sonar, which they need to detect salmon.”

But human-made noise doesn’t affect just salmon-eating orcas. Transient killer whales — a group of more than 260 nomadic whales — eat seals, dolphins and other porpoises. Due to their prey’s acute hearing, transients rarely echolocate but, instead, hunt through a stealthy game of hide-and-seek. “Transients are virtually silent while hunting, using passive listening to detect prey,” says Ford. When boats come near, transients likely can’t hear their prey splash.

Boat noise isn’t the only source of acoustic pollution. One day in the early 1980s, Ford saw orcas react to a ship’s low-frequency sonar in Johnstone Strait. “The whales had formed a tightly knit group and were heading toward the shore. I wasn’t sure whether they were going to end up on the beach.” The whales swam in dangerously shallow water until the sonar passed, at which point they returned to the deep. The orcas’ frantic reaction taught Ford that sonar has the potential to cause serious harm.

Lindy Weilgart, a marine researcher at Dalhousie University who specializes in acoustic communication among whales, believes sonar affects whales in other ways too. “There is enough evidence to show that they don’t need a beach to die,” says Weilgart, referring to a case in which a whale died at sea four hours after having been exposed to sonar. “The stimulus of the noise itself hitting the super-nitrogen-saturated blood is enough to force the nitrogen bubbles out of the solution, blocking blood vessels and causing hemorrhaging.” Boat noise, while not directly deadly, says Weilgart, still impacts the orcas’ environment. “Whales are dealing with many stressors all at once,” she notes, pointing to low salmon stocks and water pollution. “They’re rarely dealing with just noise pollution.”

Michael Jasny, an environmental lawyer for the New York City-based Natural Resources Defense Council, says sound pollution could be tackled by mandating quieter, more energy-efficient propellers on large ships. “You could save the shipping and travel industry millions,” he says. Jasny describes the whales’ acoustic environment as an “urban jungle” and warns that Canada’s small orca population could experience further decline if sound pollution isn’t confronted. “The problem will only become worse if Canada doesn’t take action.”