Whale song and the development of whale culture is a fascinating thing. Now researchers from the Wildlife Conservation Society (WCS), Columbia University and Australia have found that humpback whales from different sides of the same ocean basin are singing different songs -- an surprising finding since whales from the same basin usually sing the same tunes.
Previously, when whale songs from the same basin were compared, researchers found that the songs typically consisted of the similar parts or what is called in whale song parlance as "themes," or distinct sounds which are often repeated in cycles lasting up to 30 minutes.
Usually, songs are transmitted between different whale populations come in contact during migrations or mating seasons. However, these new findings of whales inhabiting the waters off Madagascar and Western Australia challenge previously held notions about how whale cultures spread within the same basin.
Writing in the January issue of Marine Mammal Science, lead author Anita Murray says that
In the Northern Hemisphere, within an ocean basin whales sing songs that are composed of the same themes. However, whales in the southern Indian Ocean are singing almost completely different songs. Songs from Madagascar and Western Australia only shared one similar theme, the rest of the themes were completely different.
The reason for this anomaly remains a mystery. It could be the influence of singing whales from other ocean basins, such as the South Pacific or Atlantic, indicating an exchange of individuals between oceans which is unique to the Southern Hemisphere.
More research needed
The researchers surveyed, recorded and compared the songs of 19 individual whales during one breeding season, culminating in almost 20 hours of recordings for audio-visual analysis. Out of eleven recorded themes, only one theme song was mutually existent in both populations. They're hoping to continue further studies, as WCS conservationist Salvatore Cerchio adds that
We have glimpsed here a snapshot of differences in repertoire between humpback whale populations of the Indian Ocean during a single season. Continued monitoring of these songs can provide us with valuable information on how whale songs are exchanged and how those channels of cultural transmission can be protected in the future.
More info and audio samples of whales from Madagascar and Western Australia over at WCS.