Mystery of 'ocean quack sound' solved

  • April 24, 2014
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Mystery of 'ocean quack sound' solved


A strange un­der­wa­ter sound whose source was a mys­tery for dec­ades comes from minke whales, bi­ol­o­gists have con­clud­ed. The find­ing, they say, has been ac­comp­an­ied by sur­pris­ing new facts about the whale's move­ments, and should yield more in­forma­t­ion.

The odd rhyth­mic sound was first re­ported by sub­ma­rine sail­ors in the 1960s. They called it the “bio-duck” sound be­cause they thought it sounded like a duck. Recorded since at var­i­ous loca­t­ions in the South­ern ocean, it's now be­ing at­trib­ut­ed to the Ant­arc­tic minke whale, Bal­aen­op­tera bon­ae­ren­sis. The find­ings were pub­lished April 23 in the journal Bi­ol­o­gy Let­ters.

Last year, re­search­ers put acous­tic “tags” on two Ant­arc­tic minke whales in Wil­hel­mi­na Bay off the west­ern Ant­arc­tic Pen­in­su­la. Sci­en­tists led by De­nise Risch of Na­t­ional Oceanic and At­mos­pher­ic Ad­min­is­tra­t­ion's North­east Fish­er­ies Sci­ence Cen­ter then an­a­lyzed the da­ta and iden­ti­fied the sound.

A se­ries of deep pulses, it's heard mainly dur­ing the south­ern win­ter around Ant­arc­tica and off Aus­trali­a's west coast. No one knew those whales were there. The find­ing in­di­cates some minke whales stay in ice-covered Ant­arc­tic wa­ters year-round while oth­ers make sea­son­al migra­t­ions fur­ther north, the sci­en­tists said.

“These re­sults have im­por­tant im­plica­t­ions for our un­der­stand­ing of this spe­cies,” said Risch. “We don't know very much about this spe­cies,” she added, but the tags pro­vide “an op­por­tun­ity to change that, es­pe­cially in re­mote ar­eas.”

Sci­en­tists on a hard in­flat­a­ble boat used poles to tag the an­i­mals. The tags recorded sounds, wa­ter tem­per­a­ture and pres­sure. No oth­er ma­rine mam­mal spe­cies were ob­served in the ar­ea when calls were recorded, the sci­en­tists said.

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The sci­en­tists did­n't in­i­tially rec­og­nize the mys­te­ri­ous sounds as the “bio-duck,” in­stead at­trib­ut­ing them pos­si­bly to sub­ma­rines, some ocean­o­graphic phe­nom­e­non, or even fish. They made the con­nec­tion to the “bio-duck” sound af­ter check­ing pub­lished lit­er­a­ture.

Minke whales, which have been vic­tims of Jap­an­ese whal­ing expe­di­tions, are the small­est of the “great whales” or ror­quals, a group that in­cludes the blue whale, Bry­de's whale, and hump­back, fin, and sei whales. Ror­quals are rath­er stream­lined, have point­ed heads and, ex­cept for hump­back whales, small point­ed fins.

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Source : http://www.world-science.net

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