Sperm whales seem to communicate with sequences of clicks
Amanda Cotton
Sperm whale calls are far more complex than we thought – and could be an animal communication system that is the closest thing to human language yet discovered.
The claim is based on an analysis of thousands of exchanges made by east Caribbean sperm whales (Physeter macrocephalus), which were recorded over several years.
“It’s really extraordinary to see the possibility of another species on this planet having the capacity for communication,” says Daniela Rus at the Massachusetts Institute of Technology. “We used to believe that we are the only ones.”
Sperm whales are long-lived animals with complex social lives, with females and their young living in small groups. They hunt their prey – mainly squid – using echolocation that involves streams of regular clicks. It was known that the whales often vocalise at each other with short bursts of irregular click patterns lasting a few seconds, but their significance was unclear.
“They dive together, they eat together, they hunt together,” says Rus. “There is so much collaboration and we hear their vocalisations while they do all these activities, so the question is, what does all this stuff mean?”
To investigate, Rus and her team analysed nearly 9000 sperm whale calls that had been recorded using devices stuck to the animals with suction cups, as part of a monitoring project conducted between 2014 and 2018.
Previously, it was thought that this group of whales used 21 different click patterns, known as codas. In the latest analysis, the team found that there are really 18 different basic codas, but they can be changed to give several further levels of complexity.
For instance, sometimes a known coda would have an extra click tagged on either at the start or the end – this often seemed to indicate that it was the listening whale’s turn to speak.
Another discovery is that sometimes known codas are stretched out by slowing them down while maintaining their rhythmic pattern.
Based on these findings, the researchers estimate that there are several hundred possible click patterns, although only 156 were seen in this dataset. They have drawn up a sperm whale “phonetic alphabet” to help them classify future recordings.
The whales also seem to be adding complexity by combining different codas in sequences, in the same way that human language involves adding together different letters to make words.
“Once you have this combinatorial basis, it allows you to take a finite set of symbols [and] compose them to create an infinite number of symbols by following a set of rules,” says Pratyusha Sharma, also at MIT. “Now that we have this alphabet, the next thing we’re trying to do is see how they sequence together.”
Paul White at the University of Southampton, UK, who wasn’t involved in the work, says the fact that sperm whales use these sounds for echolocation while hunting suggests they can accurately perceive small changes in the intervals between clicks. “There’s logic to assuming those intervals could convey information.”
“It’s always been a mystery how sperm whales, which have quite complex social structures, communicate with each other when their signals are boring sets of pulses,” he says. “This idea that it’s the fine structure within the codas that’s conveying the information is an interesting concept.”
If it is shown that combinations of clicks do convey a wide range of meanings, the sperm whales’ communication abilities would be unique among non-human animals.
Some other species, including various primates, can signal to each other with a small set of calls or movements. For instance, some monkeys use different alarm calls to warn each other about various predators, such as leopards, snakes and eagles, which would require different escape strategies.
But these communication systems are too limited to be classed as language, which is usually defined as unfettered expression of thoughts into signals.
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