Front pageTwice every month, Whales online selects a significant current event concerning whales and their world. 31 July 2008 Researchers interpret humpback whale soundsHumpback whales produce two types of vocalizations that are associated with distinct functions: songs and social sounds. Roger Payne's groundbreaking humpback whale studies in the 1970s revealed that they produce complex sound sequences, five to 30 minutes in length. The precisely repeated sequences were categorized as “songs”. Only males produce songs. Thus, this type of vocalization likely plays a key role for humpback whales during the mating season, either to attract females or to signal a male's presence, or both. A progression of understanding Rebecca Dunlop from the University of Queensland, Australia affirms that many researchers have looked into the structure and meaning of humpback whale songs over the years. Yet, little information has been acquired pertaining to the other, more “raw” sounds produced by humpback whales, sounds that are not songs. Dunlop and her colleagues decided to follow a humpback whale population from 2002 to 2005 as it migrated between Australia's Great Barrier Reef and the Antarctic Ocean. Their data has recently been published in the Journal of the Acoustical Society of America. A total of 660 sounds were recorded from 61 different groups. Through their three years of work with the Humpback Whale Acoustic Research Collaboration (HARC), the researchers discovered a minimum 34 different sound types, at least three times the number they were expecting. Some of the sounds endure less than one second, while others last up to 10 seconds. These sounds have been associated to specific social behaviour. The wops and the thwops The research team combined land-based observations with hydrophone recordings in order to establish correlations between sounds and social behaviour. They have discovered that the sounds humpback whales emit by blowing air through submerged blowholes is an aggressive signal often heard in groups where there is competition, when several males are available for one female. Another sound, called wop, is mainly used by females to establish contact with their calves. A similar sound, the thwop, is predominantly produced by solitary males seeking a female. Discoveries that hold promise for the future The study of whale vocalizations has conservation implications. As oceanic noise levels increase, it will be possible to evaluate the impact that this human-made noise pollution has on communication between the inhabitants of the world's oceans. [Nature News] I want to know more On the Nature News site: Marine biologists interpret whale sounds, barks and grunts hold much meaning for humpbacks. On Whales Online:
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