'Humpback and calf'
There is nothing more exciting to the cruising sailor than the near sight (as long as not TOO near) of a whale blowing watery mist into the air with their unmistakable throaty blast. Their singing is legendary, previously thought only to be in the breeding season. However a new Antarctic study suggests that they also sing 'intensely and continuously' while engaged in other tasks or a combination of activities - diving and foraging as well as breeding.
Here is part of the report, published on the primary scientific research site, Plosone:
Reports of humpback whale (Megaptera novaeangliae) song chorusing occurring outside the breeding grounds are becoming more common, but song structure and underwater behavior of individual singers on feeding grounds and migration routes remain unknown.
Ten humpback whales in the Western Antarctic Peninsula were tagged in May 2010 with non-invasive, suction-cup attached tags to study foraging ecology and acoustic behavior. Background song was identified on all ten records, but additionally, acoustic records of two whales showed intense and continuous singing, with a level of organization and structure approaching that of typical breeding ground song.
The songs, produced either by the tagged animals or close associates, shared phrase types and theme structure with one another, and some song bouts lasted close to an hour. Dive behavior of tagged animals during the time of sound production showed song occurring during periods of active diving, sometimes to depths greater than 100 m. One tag record also contained song in the presence of feeding lunges identified from the behavioral sensors, indicating that mating displays occur in areas worthy of foraging.
These data show behavioral flexibility as the humpbacks manage competing needs to continue to feed and to prepare for the breeding season during late fall. This may also signify an ability to engage in breeding activities outside of the traditional, warm water breeding ground locations.
'They need to feed. They need to breed. So essentially, they multi-task,' said study co-author Ari S. Friedlaender, research scientist at Duke University's Nicholas School of the Environment. 'This suggests the widely held behavioral dichotomy of breeding-versus-feeding for this species is too simplistic.'
Humpbacks sing most frequently during breeding season, but are known to sing on other occasions too, such as while escorting mother-calf pairs along migratory routes. Though the reasons they sing are still not thoroughly understood, one distinction is clear: Songs sung in breeding grounds are quite different in duration, phrase type and theme structure from those heard at other locations and times.
'The fact that we heard mating displays being sung in late-season foraging grounds off the coast of Antarctica suggests humpback whale behavior may be more closely tied to the time of year than to physical locations. This may signify an ability to engage in breeding activities outside their traditional warm-water breeding grounds,' said Douglas P. Nowacek, Repass-Rogers University Associate Professor of Conservation Technology at Duke's Nicholas School.
To download an audio of whale 'songs' from Plosone, click here.
by Plosone/Sail-World Cruising
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11:46 PM Fri 21 Dec 2012GMT
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