Humpback whale populations in the Atlantic and Indian Oceans are picking up musical ideas from one another, and incorporating the new phrases and themes into their songs.
Whale populations in different Southern Hemisphere ocean basins sing similar song types, but the amount of similarity differs across years. This suggests that males from these two populations come into contact at some point in the year to hear and learn songs from each other.
The humpback whale grows up to 50 feet in length and has been globally protected from commercial whaling since the 1960s. The Wildlife Conservation Society describes male humpback whales as some of the animal kingdom's most noteworthy singers:
Individual animals sing complex compositions consisting of moans, cries, and other vocalizations called song units. Song units are composed into larger phrases, which are repeated to form themes. Different themes are produced in a sequence to form a song cycle that are then repeated for hours, or even days. For the most part, all males within the same population sing the same song type, and this population-wide song similarity is maintained despite continual evolution or change to the song leading to seasonal hit songs. Some song learning can occur between populations that are in close proximity and may be able to hear the other population's song.
Researchers detected shared phrases and themes in both populations that developed over time. One of the shared themes, however, had differences. A Gabon version of Theme 1 consisted of a descending cry-woop, whereas the Madagascar singers split Theme 1 into two parts: a descending cry followed by a separate woop or trumpet.
Other differences emerged. The song sung by whales in Gabon became more elaborate than their counterparts in Madagascar. Both population song types shared the same themes, with the whales in Gabon's waters singing three additional themes. Eventually, songs sung on both sides of Africa were largely similar, with individuals in both locations singing songs with the same themes and order.