This Sperm Whale Relocation Is Further Evidence They Have a ‘Culture'
Two vocal clans around Galápagos took up and left. Others moved in.
Galápagos sperm whale. Image: Mauricio Cantor, Whitehead Lab, Dalhousie University
Do sperm whales have a "culture" of their own? Shane Gero, a Canadian marine biologist based at Aarhus University's Marine Bioacoustics Lab in Denmark, thinks so. He's spent over a decade following the same individual whales around the Caribbean island of Dominica, and has found that sperm whales have a set of traditions, including dialects, that vary among their clans.
These "vocal clans" are defined by the codas (or recognizable patterns of clicks) they emit to communicate with one another. Each clan performs its codas somewhat differently, and is socially segregated from the others, he said.
A new paper from Gero and co-authors seems to give further heft to the argument that sperm whales have a culture—even a "civilization," as he has called it—of their own. The researchers traced how two "cultural groups" of sperm whales near the Galápagos Islands relocated, and two completely new whale clans later moved in.
Although it's impossible to say for sure why these groups of whales were uprooted, to Gero it's another sign of the strong cultural bonds that keep sperm whale clans together. Instead of adapting their culture to whatever changes prompted them to leave, they relocated themselves."These cultures are a significant part of their lives, and it would appear, their identity," he told me. "That's not so easily given up. Even though there seems to be this large-scale displacement, they retain their culture. It's a part of who they are."
In the study, led by Mauricio Cantor at Dalhousie University and published in the journal Royal Society Open Science, the researchers started out by identifying two clans of whales near Galápagos, in the Pacific. (While the males can rove solo over thousands of kilometres, matrilineal sperm whale societies tend to show regional affiliations, Gero explained.) One clan tends to perform a coda called "Regular," for a regularly spaced series of clicks, and the other "Plus-One," with a longer pause before the last click.
These two clips serve to demonstrate the differences in the coda types produced by the Regular and Plus One Clans. Audio (both files above): Luke Rendell, University of St. Andrews
Between 1985 and 1999, scientists identified and documented whales through photographs. The animals' numbers declined through the nineties. They were gone by 2000, and seem to have moved further east, to coastal waters, for reasons that aren't clear. (The researchers hypothesize that climate change, or the legacy of whaling, may have played a role.)
In 2013 and 2014, scientists reassessed the population in this part of the Pacific, and found 463 new females. But they didn't see any matches with the whales identified from 1985 to 1999. The codas, called "Short" (producing brief codas with fewer than five clicks) and "Four-Plus" (whose codas have a base of four regular clicks, according to the paper) displayed by new whales were rarely or never heard before in the Galápagos before this. But they had been heard from other whales elsewhere the Pacific.
In other words, two clans of whales moved away, and other clans moved in.
Gero calls it a "physical and geographical movement of cultures," akin to the great migrations of humans. Among animals, population numbers can go up and down, but a "cultural turnover" like this hasn't been documented outside of humans, he continued.
What's significant to Gero is that, once the whales moved to a new place, they retained their markers of "culture," including dialect and foraging habits that define their groups as distinct from one another. "It suggests that culture is critically important to them," he said. These whales would rather uproot and establish themselves in a new area to "maintain their culture," he continued, rather than "adapt it to a changing environment."
Gero has argued that whales' "culture" should be taken into account when tackling the problem of how to conserve the species, which is critical given the pressures they're under. "The critical diversity in sperm whale life, as in our own, is found in their cultures," he told me in a follow-up email.
"With environmental changes we expect, whether it's climate change or our increasing presence in the ocean, there may come a time where they don't have a place to go," Gero said.
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