Social insights from whale chatter
- 9 September 2015
- From the section Science & Environment
Scientists think they have new insights into the different dialects used by groups of sperm whales.
These great beasts live in very tight social networks, chatting amongst each other using a system of clicks.
The researchers have shown how separate clans - perhaps numbering thousands of animals - will use their own particular subtle sequence of noises.
These vocalisations are not innate - they must be learned, the team writes in the journal Nature Communications.
And the scientists argue that this indicates the whales are behaving in ways that at some level mirror the operation of human cultures.
The study was led from Dalhousie University in Halifax, Canada. It investigated sperm whales swimming off the Galapagos Islands in the eastern Pacific.
Two frequently observed clans were seen using distinct click repertoires, or codas.
"These codas sound like Morse code - patterns of three to 12 or 15 clicks that vary in rhythm and tempo," explained PhD student Maurício Cantor.
"In one clan we call the 'regular clan', we heard regularly spaced clicks, but in another vocal clan that we call the 'plus-ones', the coda types they make have an extended pause at the end before the last click."
And the two clans do not mix, added Prof Hal Whitehead, also from Dalhousie.
"They behave differently; they move around differently; they babysit their babies differently," he told the BBC. "And so while a family unit from the regular clan will get together with another family unit from the same clan, sometimes for days - and the same for the plus-ones - we've never seen a regular unit associate with a plus-one unit."
The scientists wanted to understand how the different vocal clans might emerge; they wanted to assess whether the types of codas being used could have a simple genetic origin, or whether they had to be cultural in origin.
And one of the lines of inquiry was to build a computer model.
"We basically created a virtual population of whales and made them live according to the biological rules of the real world," Mr Cantor said.
"In one of our scenarios, we had genetic transmissions of codas from mothers to their calves; and in other scenarios we had whales creating their vocal repertoires on their own or learning from each other.
"And our results suggest only when we have whales learning from each other, or copying bits of their coda types, can we have, over time, these different dialects."
The different codas cannot be driven by geographical separation - as sometimes seen in song birds - because the whales' great ranges mean clans will always encounter one another. Furthermore, the level of sophistication in the repertoires hinted strongly at the idea that the codas are learned, stressed Prof Whitehead.
"Having spent a lot of time out there with them, it's become clear to me that in many ways sperm whales are even more social than us," he said.
"They have little permanent in their environment except each other. They depend on each other for all kinds of things. You can see it - they touch each other a lot; they nuzzle. And being vocal creatures, it's not surprising they use sounds a lot.
"And when our colleagues examined how these sounds were made, it looks like a primary function of these codas is social bonding, reinforcing the bonds that exist between the whales," he explained.
"A second function is to indicate 'we are all the same social unit because we work together and we have the same dialect', but also, at a larger scale, to say 'we are part of the same clan' - and that may include thousands of whales who all see themselves as part of the same large social grouping."
Prof Whitehead likened this to football supporters wearing their team's colours. They might not know everyone in the stadium, but they self-identified and sang the same songs.
You can hear more from the Dalhousie team this week - in the UK on BBC Radio 4's Inside Science programme with Tracey Logan, and globally on the BBC World Service's Science In Action programme with Jack Stewart.
and follow me on Twitter: @BBCAmos