Hundreds of recordings of humpback whale songs have shown that their sound becomes more complex over time and is experiencing "cultural revolutions" with an abrupt change of "melody" to a new, simple and popular one.
Humpback whales are migratory creatures, they spend the summer in the polar seas feeding on the rich resources of krill, and by winter they overcome thousands of kilometers to equatorial waters, where females bring their calves. And all this time they are actively communicating: their songs are almost the most diverse and complex among all the whales. Different populations use different songs, gradually changing over time. Moreover, biologists from the University of Queensland in Australia have shown that they are not only changing, but becoming more complex and going through "cultural revolutions." Jenny Allen and her colleagues write about this in an article published in the journal Proceedings of the Royal Society B: Biological Sciences.
Indeed, the songs of humpback whales are one of the clearest examples of the existence of "cultures" in animals. As with us, they are passed from population to population, mix, spread and are forgotten. Scientists have traced how the songs of whales migrating across the east coast of Australia changed during 2002-2014. In total, spectrograms of 412 songs by 95 "performers" were obtained. Biologists estimated the duration of each song, the variability of its "melody", the number of repetitions, and the like, calculating the conditional complexity. It turned out that over time this indicator is steadily increasing, year by year it becomes longer and more diverse.
At the same time, from time to time, whale populations go through the stage of the "cultural revolution" with a sharp change of song and the beginning of a "fashion" for a new one. At first, it is still short and simple in structure, but it also becomes more complicated over time. The new "fashion" holds and develops for several years, until the East Australian humpback whales hear the next melody, meeting with fellows from the west. Scientists believe that these processes are associated with the desire of each whale to add its own notes to the performance of a common song. Gradually accumulating additional elements, its sound changes and becomes more complex. This happens up to the moment when it is replaced by a new song: its melody has not yet acquired many additions, it is simple and easy to "improve".