Dolphins have local accents on either side of New Zealand

Regional accents aren’t just human: bottlenose dolphins have them, and new research shows they can be different even between two populations whose separation is not insurmountable.

The New Zealand accent is so distinctive that the national airline has made its incomprehensibility a hallmark of its advertising. However, that may not matter to the dolphins, who may have difficulty communicating with those living on the other side of the country. We don’t know for sure – maybe they’re just mocking each other mercilessly even though they know what’s being said – but they certainly sound very different.

Dr. Jessica Patiño-Pérez of Massey University recorded the whistles used by bottlenose dolphins on Great Barrier Island (GBI) off the north coast of New Zealand, Aotearoa. She received recordings from another population in Doubtful Sound (DS) near the southern tip of the South Island from Dr Marta Guerra of Otago University, which would be the local campus of the DS dolphins if dolphins went to university.

Patiño-Pérez worked with colleagues from her own university to analyze these and compare them with dolphins recorded around the world.

Dolphins are very talkative animals, using sounds to find food and maintain group cohesion. Whistles, with frequencies between 3,000 and 36,000 Hz and lasting up to four seconds, are just one of three types of sound used to talk to each other.

The local environment can influence whistling: dolphins that live in deeper water use lower sounds than dolphins that are more coastal and can afford the high-pitched sounds that cannot travel as far. Dolphins have so-called ‘signature whistles’, which are thought to be equivalent to their name, a way of identifying themselves with others in the group. The team ignored these and focused on the common whistles used by many or all group members.

It has already been established that dolphins use whistles to coordinate behavior, recognize each other and generally maintain harmony. That all depends on the ability to understand what a particular whistle means. If populations become isolated from each other long enough, it’s natural that their languages ​​will drift, just as human speech does.

What we don’t know, however, is how long it will take before this reaches the point where different groups of dolphins can no longer understand each other. Genetically, the GBI and DS populations are known to be largely different, so it appears they haven’t mixed much in a long time.

This is certainly reflected in their communication: whistle contour, duration and final frequency vary widely between the two groups. The sounds the team recorded are so different that computer programs can identify with 90 percent accuracy which population the whistles come from. “The main differences were the contours of the whistle type, duration and final frequency,” the authors write.

“Whistles from DS had a longer duration and had more inflection points than whistles from GBI,” the authors write. “On a global scale, the acoustic parameters of New Zealand population whistles clustered with populations in the Northern Hemisphere, rather than with those in the Southern Hemisphere.” Perhaps Aotearoa’s waters were colonized along with its lands by imports from the north.

Curiously, despite living in shallower waters, GBI dolphins are the ones that use lower frequencies, although the vocal ranges of most populations overlap. The authors speculate that the DS dolphins may have changed their tune in response to the number of boats at the popular tourist spot.

We still don’t know whether bottlenose dolphins from one population could understand a member of the other population if it came into their territory, or whether they would just joke about it for whustlun stringe. However, it is possible that mutual misunderstanding will increase geographical divisions. There is no point in making contact with a strange dolphin if he does not understand what you are saying.

The research has been published open access in the New Zealand Journal of Zoology.

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