sábado, 27 de octubre de 2007

Whale watchers noise

Din among the Orcas: Are whale watchers making too much noise?

Susan Milius

Whale-watcher boats may be making so much noise that killer whales off the coast of Washington have to change their calls to communicate over the racket.


WATCH OUT. Whale watching has become so popular that 22 tourist boats, on average, attend a pod of killer whales off the Washington coast.
F. Felleman

Recordings made during the past 3 years, after a boom in whale watching in Washington State, show that killer whales lengthen a characteristic call by about 15 percent when boats cluster around them, reports Andrew D. Foote of the University of Durham in England.

Recordings from earlier eras, when there were fewer whale watchers, showed no link between call length and the presence of boats, say Foote and his colleagues in the April 29 Nature. They suggest that boats following the whales may not interfere with animal communication until some critical number of churning engines makes the noise just too loud.

That change "is certainly a red flag," contends coauthor Rus Hoelzel, also of Durham. "Maybe we ought to think about fewer boats."

People naturally adjust their voices to make themselves understood over background noise, and research suggests that animals do the same. Humpback whales lengthen their calls during playback of low-frequency active sonar, and in the July 17, 2003 Nature, researchers in the Netherlands reported that city birds near heavy traffic tend to sing at higher pitches (SN: 7/19/03, p. 37: http://www.sciencenews.org/articles/20030719/fob5.asp).

The killer whale–research team analyzed recordings from three pods, or maternally related whale groups. In these pods, which live off the Washington coast, "everybody seems to stay home with Mum," says Hoelzel. "There are males we saw born 30 years ago, and they're still there."

Each pod has its own distinctive primary call, which accounts for more than half the vocalizations and may coordinate foraging. Foote describes the three pods' calls, respectively, as sounding like a train whistle, a kitten mewing, and a slide whistle. The researchers compared the length of these calls, with and without boats present, in recordings from 1977 to 1981, 1989 to 1992, and 2001 to 2003.

The only difference in call length turned up in the last period. During the 1990s, the average number of vessels clustering around a pod of whales increased roughly fivefold, and it now averages about 22. This whale population has been declining since 1996, but biologists aren't sure why.

"One thing I want to make clear is that I think whale watching is a good thing," says Hoelzel. It just may need tighter regulation, he explains.

Roger Gentry, who directs acoustics studies of marine mammals for the U.S. National Oceanographic and Atmospheric Administration, says he certainly finds it plausible that killer whales would compensate for underwater clamor. However, the meaning for the whales of the increase in call length isn't yet clear. "We have to keep watching," he says.


In this article Rus Hoelzel states, "One thing I want to make clear is that I think whale watching is a good thing." He then states that the activity may just need "tighter regulations." I feel that this argument isn't valid. If whale watching is causing danger to the species, then it's not good. Whales should have the right to live in peace. If people want to whale watch they should find a safer way to do it, perhaps from shore.

Erica Hodge
San Ramon, Calif.

If the engines of whale-watching boats are disturbing the Orcas, why not switch the boats to sail power? Surely, this means of locomotion would also provide a better experience for the whale watchers.

Lorien Davy
Santa Barbara, Calif.


Foote, A.D., R.W. Osborne, and A.R. Hoezel. 2004. Whale-call response to masking boat noise. Nature 428(April 29):910. Abstract available at http://dx.doi.org/10.1038/428910a.

Further Readings:

Milius, S. 2003. Bad bubbles: Could sonar give whales the bends? Science News 164(Oct. 11):228. Available to subscribers at http://www.sciencenews.org/articles/20031011/fob3.asp.

______. 2003. City song: Birds sing higher near urban traffic. Science News 164(July 19):27. Available at http://www.sciencenews.org/articles/20030719/fob5.asp.

Miller, P.J., et al. 2000. Whale songs lengthen in response to sonar. Nature 405(June 22):903. Abstract available at http://dx.doi.org/10.1038/35016148.

For further information on killer whales, go to http://nmml.afsc.noaa.gov/education/cetaceans/killer2.htm.


Andrew D. Foote
School of Biological and Biomedical Sciences
University of Durham
Durham DH1 3LE
United Kingdom

Roger Gentry
NOAA Office of Protected Resources
1315 East-West Highway
Silver Spring, MD 20910

A. Rus Hoelzel
School of Biological and Biomedical Sciences
University of Durham
Durham DH1 3LE
United Kingdom



From Science News, Vol. 165, No. 18, May 1, 2004, p. 275.

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