Whales are known to have different cultures, in which different groups sing and communicate using different songs. This is the case with the sperm whales that live off the Galápagos Islands in the Pacific, but in an interesting set of events reported in the Royal Society Open Science, it seems that one group of whales completely replaced another, something that hasn’t been observed before in the species.
What seems to have occurred is a large scale migration of different groups, or “clans”, of sperm whales. When the two original groups moved out of the waters surrounding the Galápagos, it turns out that it wasn’t the same whales that returned over 10 years later. This cultural turnover, in which “an entire population is replaced with a completely different set of individuals,” according to the authors of the study, is actually a very rare event, and has usually only been witnessed in human societies.
It all began when researchers from an international group of universities started studying the sperm whale population living off the Galápagos Islands in 1985. Using photo identification and sonar microphones, they were able to track individual whales and determined that there were two distinct clans, which communicated between themselves in distinct vocalizations or dialects. These were the Regular clan, which communicated with regularly spaced clicks, and the Plus-One clan, which showed an extended interval before the last click.
But then in the 1990s, something happened. For some unknown reason, both clans of whale started to leave the Galápagos, and headed for the coast of Chili and the Gulf of California. By 1999, there were no sperm whales left in the waters surrounding the remote Pacific islands. What drove this sudden movement is still not understood, but it is thought that it may have been to do with the availability of their favorite food, squid. Either the numbers dropped around the islands, or they increased along the coast of the mainland.
That was until the researchers heard reports in 2013 of sperm whales having been spotted off the Galápagos Islands once more. Heading back out, they lowered their sonar microphones into the waters and expected to hear the two clans once again chatting. But what they heard was different. The ocean was now filled with the noises of two different clans, which are known as the Short clan, and the Four-Plus clan. These groups had been heard before in other parts of the Pacific, but were rare visitors to the Galápagos.
It seems then that the original two clans of whales have now been superseded by two completely different groups. This total cultural turnover, in which not a single member of either of the first groups integrated into the second groups is surprisingly rare within the animal kingdom, and could have significant implications on how people manage sperm whale populations in the future.