A new study documents the movement of humpback whale songs across six whale populations in the Pacific—a feat of cultural transmission described as “unparalleled in any other nonhuman animal.”
Within a given humpback population, male whales (only the males sing) adopt the same mating song, with only minor variations. These songs can be enormously complex, made up of numerous themes that are repeated in the same order. From 1998 to 2008, the researchers identified 11 distinct songs.
A population can stick with the same song for several years before suddenly switching to a new one; alternatively, a song might gradually evolve until it counted as new. The researchers were especially struck by the way populations picked up the songs from adjacent populations, despite very little intermingling. (The populations are genetically distinguishable.)
For as-yet-unexplained reasons, songs almost always moved eastward. (The simplest explanation, though hardly a comprehensive one, is that the largest population of whales examined is the one just off Australia, so there are more whales to spread the word.) One coded as the “blue” song proved especially viral: It evolved off Eastern Australia, from an earlier song, in 2000, before sweeping through populations near New Caledonia, Tonga, American Samoa, the Cook Islands, and French Polynesia, which it reached in 2004—a 4,000-mile journey.
Another song spanned two ocean basins: First detected in the Indian Ocean in 1995, it has also been heard in French Polynesia.
“Humpback whale song is unique because intense conformism to the current (song) norm is coupled with high plasticity in the trait,” the authors write. “Why both plasticity and conformity might be selected, how these interact with sexual selection, and how cultural evolution inﬂuences both are intriguing questions in need of attention. ”
Source: “Dynamic Horizontal Cultural Transmission of Humpback Whale Song at the Ocean Basin Scale,” Ellen C. Garland, Michael J. Noad, Anne W. Goldizen, and seven other authors, Current Biology (April 26)
Via Wired Science, which includes recordings of the some of the songs studied.