Humpback whale song is identifiable because of its intricate pattern of structure. These whales compose their songs for the purposes of breeding, learning new songs as they come in contact with fellow crooners.
Exactly how and when humpback whales learn these songs, however, remains a larger mystery. Recordings reveal a possible link between three distinct breeding populations off the shores of eastern Australia and the island to the east of New Caledonia with a shared feeding ground in Antarctica.
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Songs From The Sea
Imagine a world where sight is limited by the extreme scattering of photons and smell is ineffective due to lethargic diffusion of molecules slowed by the density of water.
In these conditions both sight and smell are limited. These conditions characterize, among other things, the ocean, where large sea mammals rely mostly on sound to communicate. The speed of sound is four times greater in water than in air at sea level. Male humpback whales have been observed communicating via ever-changing patterns of vocalization, which scientists have termed ‘song’.
A Song For Every Occasion
These whales compose their songs for the purposes of breeding, learning new songs as they come in contact with fellow crooners.
Exactly how and when humpback whales learn these songs, however, remains a larger mystery. To dive more deeply into the nebulous realms of humpback whale song sharing, researchers of a recent PLOS ONE study recorded instances of humpback whale song in the Southern Ocean
Humpback whale song is identifiable because of its intricate pattern of structure. Songs are composed of multiple sound types, for example, as these researchers suggest, ‘ascending cry,’ ‘moan,’ and ‘purr’.
When units come together to form a pattern, these units form a phrase. Phrases repeated become a theme, and themes sung in a particular order compose a song. Researchers recorded these compositions by deploying radio-linked sonobuoys, which transmit underwater sound, and then digitized the recordings.
Here is an example of song recorded off the coast of New Caledonia in 2010.
A Breaching Humpback Whale
Humpbacks frequently breach, throwing two-thirds or more of their bodies out of the water and splashing down on their backs.
A Traveling Song
Recordings reveal a possible link between three distinct breeding populations off the shores of eastern Australia and the island to the east of New Caledonia with a shared feeding ground in Antarctica.
In early 2010, the researchers identified four songs near Antarctica that matched themes from eastern Australia in 2009. By July, 2010, all four songs were then also identified in the group from New Caledonia. The themes recognized in New Caledonia in 2010 were entirely different than the themes of 2009, suggesting a movement of new songs eastward from eastern Australia to New Caledonia.
Consequently, the shared feeding grounds in Antarctica used by both the eastern Australia and New Caledonia groups in early 2010 may be the point at which these populations’ songs diverged.
In addition, the inclusion of feeding grounds into the dynamic pattern of humpback whale song sharing helps shed new light on overall patterns of song learning and transmission from one breeding group to another.
Humpback Whale Amidst Icebergs
Sound recording off the Balleny Islands near Antarctica, however, is challenging, and the sample of whale singers from this area remains relatively small.
Regardless, the song documented here suggests Antarctica as an emerging location for future study, and highlights the importance of feeding grounds in the transmission of humpback whale song. Through a better understanding of how and where these dynamic compositions radiate across the Southern Ocean, we can begin to understand humpback whale population connectivity and one of the best examples of non-human, large-scale learning demonstrated throughout the Southern Hemisphere.
This article originally appeared on PLOS.org.