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Beaching It

September 3, 2012

Torah Kachur

The mass stranding of 13 pilot whales off the coast of Britain on Sunday and 22 pilot whales on the Florida coast has highlighted an all-too-common occurence of cetacean-suicide.  Over 2,000 dolphins, porpoises and whales get beached every year and die from dehydration or suffocation as high tide covers their blowholes. 

 

Whale stranding Science in Seconds Torah Kachur

 

Is this behaviour lemming-esque self-culling?  Or is it tragic evidence that humans, once again, are destroying the ocean?

 

The most prevalent hypothesis is that the sonar used by ships disrupts whale navigation and gets them confused and lost and they end up beached.  Other hypotheses include that a sick or diseased cetacean will run itself aground as its death dance but the solidarity of the pod drags the other down with it.

 

The sonar hypothesis has been gaining ground over the years - a paper published in 2009 studied the incidences of beaked whale strandings since 1847 and 126 of the 136 recorded mass deaths were since 1950 and, you-guessed-it, the advent of naval sonar.  Similarly, reports from the North American Veterinary Conference record that, in the Pacific Northwest, 1.5 average strandings per year were recorded during the 1930's through 1970's.  Now, there are an average of 36 strandings per  year.  This may be due to whales getting really stupid all of a sudden, or something fishy is going on.

 

ResearchBlogging.org It is likely that cetaceans, like any sane creature, wants to die on a beautiful beach if they are old, diseased and dying.  But there is something to this whole sonar business that someone needs to sound the alarm a little more actively.  The US Navy's most common form of sonar is in the mid-range emitting sounds of 3-8kHz, a range that has been known for some time to cause mass strandings.  The species studied most is the beaked whale for its incredibly long dive time and depth of dive.  Frequencies emitted by the ship is strong enough to rupture ear drums if the whale passes within tens of meters from the ship.  More likely though, is that the sounds emitted cause changes in the dive behaviour causing the whales to dive too deep too fast, or surface too quickly which causes the bends. 

 

*sigh.... Yet another way we are destroying the planet.  This time, the perpertrators are well aware of the effect, the battle between environmental groups and the US Navy went all the way tot the Supreme Court.  The ruling?  The US Navy can keep doing what it's doing, because it's the US Navy, and should maybe think about possibly changing it's behaviour so it stops killing some of the most beautiful and intelligent creatures we have on the planet.  The result?  No reported change in sonar use.

 

Tyack PL, Zimmer WM, Moretti D, Southall BL, Claridge DE, Durban JW, Clark CW, D'Amico A, DiMarzio N, Jarvis S, McCarthy E, Morrissey R, Ward J, & Boyd IL (2011). Beaked whales respond to simulated and actual navy sonar. PloS one, 6 (3) PMID: 21423729

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