A complex composition
Humpback whale songs are not just random sounds; they are elaborate, repeating patterns of 'units' that build into 'phrases,' which then combine into 'themes.' A single song can last for twenty minutes and is repeated for hours. The songs exhibit structure and complexity that only appear in human music or language. We know the details of these songs because of underwater hydrophone recordings that have been collected since the 1960s. By visualising these sounds as spectrograms—charts that show frequency over time—researchers have been able to map the exact structure of these songs, revealing a level of intentionality that is rarely seen elsewhere in the animal kingdom.
Cultural evolution
Perhaps the most fascinating aspect of humpback song is that it evolves. A population of whales in a particular region will gradually change their song over time, with every male adopting the new variations. Even more remarkably, new 'cultural' elements can spread from one population to another when whales from different regions encounter each other during migration. Research led by Ellen Garland has tracked these songs across the South Pacific, showing how themes move like musical trends across the ocean. This is clear evidence of cultural transmission: the song is not genetically hardwired, but is learned through social interaction, a process we usually associate with human history.
The physics of the ocean
Why do they sing so loudly and at such low frequencies? Sound travels four times faster in water than in air, and low-frequency sounds can travel for hundreds, sometimes thousands, of kilometres through the ocean's 'SOFAR channel'—a layer of water where sound waves are trapped and refracted. This allows whales to communicate across vast oceanic basins. This physical reality dictates how and when they sing. Scientists use sound-propagation models to calculate the potential range of these songs, confirming that they are designed to exploit the ocean's unique acoustic properties to reach audiences that might be incredibly far away.
The impact of noise
Modern industrialisation has filled the oceans with human noise. Shipping, oil drilling, and sonar pulses create intense acoustic 'smog' that overlaps with the frequencies humpback whales use for communication. Research has shown that when background noise levels rise, whales change their song, singing louder or shifting their frequency—a behaviour known as the Lombard effect. This stressor has real consequences for their social lives and mating success. By comparing recordings from decades ago with today, researchers have been able to measure the impact of human activity on whale communication, highlighting how even distant, unseen industries have a direct effect on marine life.