“A special kind of beauty exists which is born in language, of language, and for language.”
– Gaston Bachelard
I have always been a good eavesdropper. For an energetic (read: obnoxious) little kid, I was surprisingly good at making myself as small and quiet as possible when adults were talking. I got a certain sense of pride out of being able to piece together what they were saying, especially when they didn’t know or want me listening. It’s no surprise (at least to my family) that I found my way to sperm whale bioacoustics.
Sperm whales are one of the most widely distributed species on the planet. Among mammals, their range is rivaled only by humans and orcas. There is a clear sex bias in this distribution, with males encountered as far as the poles but females and juveniles generally restricted to more tropical regions (they seem to prefer water temperatures above 15°C—who can blame them?).
The males, with their solitary lifestyles and much larger ranges, are more difficult to observe, so much of what we know about what life is like for a sperm whale comes from studying groups of ladies and babies (although exciting research on male sperm whale range and sociality is currently being done in Japan). From the females and their young, we’ve learned that sperm whale social structure is hierarchical. At the base of this hierarchy is the social unit: groups of about ten whales who are often (but not always) related and typically stay together for life (while males fly the coop in their teens, females remain in their mom’s social unit). Different social units will swim together for hours to days at a time, forming groups. Importantly, social units of whales will only form groups if they belong to the same vocal clan, meaning that they speak the same dialect. In my last blog, I talked about what dialects—variants of a language that are particular to a specific region or social group—look like in humans. But what do we mean when we say that sperm whales have dialects too?
In social situations, sperm whales communicate using patterned series of clicks (think Morse code), called codas. Codas generally have three to twelve clicks, but the rhythmic pattern of those clicks differs depending on which vocal clan you belong too. For example, the ‘Regular’ clan (which was first described off the Galápagos Islands) makes codas that have equal spacing between each click. A different Galápagos clan, the ‘Plus One’ clan, makes codas that have equal spacing between each click up until the final click, which comes after an extended pause (my supervisor, Dr. Hal Whitehead, has likened this pause to how Canadians add ‘eh?’ to the ends of sentences, which is a fantastic analogy). Can you hear these rhythmic differences in the recordings below? All of the codas a clan uses make up that clan’s dialect.
‘Regular’ clan:
‘Plus One’ clan:
For better or worse, humans often use dialects to tell ‘us’ versus ‘them’, and sperm whales may do the same. Whales from different vocal clans never interact, even if they are sympatric, meaning that they share the same waters. So far, sympatric vocal clans have been found off the Galápagos Islands, Dominica, Mauritius, Brazil, and Japan. In places where the vocal clans have been studied in more detail, like the Galápagos Islands, we know that in addition to speaking differently, clans also forage, move, and socialize differently. Taken together, the evidence strongly suggests that each vocal clan is a distinct sperm whale culture.
With vocal clans now documented in the Atlantic, Pacific, and Indian Oceans, it’s clear that no matter where you are in the world, culture is a defining part of what it means to be a sperm whale. But how many sperm whale cultures exist worldwide? Which parts of the world have more sympatric clans, and which parts have fewer? Why should we care that sperm whales have culture at all? What do we stand to lose if a culture goes extinct? These are questions I’ve spent a lot of time thinking about and will dig into in my final blogs. I think the answers emphasize that sperm whale dialects have a “special kind of beauty” and deserve a special kind of protection.
Photo credit: Rui Roda on Flickr
