GREEN ISSUE: Endangered whales may be threatened by a noisy side-effect of globalization
GREEN ISSUE The tiny, rigid-hull inflatable boats that researchers at Scripps Institution of Oceanography use for whale tagging are a mere fraction of the size of the blue whales they are deployed to search for. But Scripps PhD candidate Megan McKenna says there's no reason to worry about the mammoth creatures — which can weigh as many tons as 27 elephants put together — bumping up against the boat when she reaches overboard with a pole to tag them.
"They're just pretty mellow, I guess," McKenna says. "There's no flailing or anything. Some barely even notice that we're there." For two summers, she's ventured out in pursuit of the endangered whales, popping short-term monitoring tags on them to learn how they behave when massive cargo shipping vessels motor past.
It's an important question for a couple of reasons. Government funding was provided for the Scripps study after two blue whales were struck and killed by commercial shipping vessels in 2007, tragedies magnified by the fact that the marine mammals are still struggling for survival. If even two die in such collisions every few years, the entire species could be imperiled, McKenna says.
At the same time, a less-understood phenomenon has marine scientists worried that the deep-blue giants' survival is being undermined by a subtler problem, that Jackie Dragon of San Francisco-based Pacific Environment likens to "death by a thousand cuts." Noise generated by whirring ship propellers registers at the same frequency as the low tones whales use to communicate and forage for food, and researchers are concerned that the constant interruption is affecting their ability to engage in basic survival behavior.
Put together with an array of concerns including chemical pollution, marine debris, over-fishing, and ocean acidification, noise pollution is just coming onto the sonar of local marine sanctuary councils and federal environmental agencies, and proposed solutions are only in the fledgling stages.
Pacific Environment is one of several environmental organizations advocating for shipping vessels to travel at slower speeds, a quieter practice that also reduces the chances of hitting a whale. Despite growing evidence that noise pollution and ship strikes pose big problems for the planet's largest mammals, it's likely to be an uphill battle in an growing global industry where time is money, and on-time delivery is paramount.
Endangered whales favor the Gulf of the Farallones and Cordell Bank sanctuaries, not far from San Francisco, so Pacific Environment has chartered a catamaran to take ecologically-minded whale watchers out to what Dragon dubs the "Yosemites of the sea." Using hydrophones, they capture the deep, rumbling whale calls. They also pick up noise generated by commercial ships, whose designated lanes cut directly through the protected areas.
Under just the right ocean conditions, the low, eerie mating call of a male blue whale off the coast of California can be heard by a female off the coast of Hawaii. "That just has to do with the physics of sound in the ocean," McKenna explains. "They're vocal animals. You can think of sound in the ocean as our vision. Sound travels so much better in water than light does, so it's really an acoustic environment that they're living in."
McKenna is working with whale researchers John Calambokidis of the Cascadia Research Collective and John Hildebrand of Scripps Institution. While they've observed that some whales linger at the surface longer than usual after a ship has passed, leaving them vulnerable to a strike, there are no conclusive results as of yet.