Dolphins remember friends up to 20 years after they last saw them, according to an American scientist who carried out research on the subject while completing his PhD at the University of Chicago. It’s all done by something called a signature call, which is a unique whistling sound each dolphin emits when it sees another dolphin.
Each dolphin’s signature call remains the same from when the dolphin is a baby right through its life, so a 20-year-old dolphin could technically remember a childhood friend, even if it hadn’t seen him in almost two decades.
The scientist who is responsible for the dolphin study, Jason Bruck, says this type of study has also been done on elephants and primates. Previously it had been thought elephants have the longest memory of any non-human species but, according to Bruck, this study proves the memory of dolphins is even more long lasting.
Dr Bruck added: ‘When they hear a dolphin they know, they often quickly approach the speaker playing the recording.
‘At times they will hover around, whistle at it, try to get it to whistle back.’
The study was undertaken by recording the signature calls of 53 bottlenose dolphins that were living in captivity in various areas of the world. All of the dolphins had spent time with other dolphins in the program years before.
The research was then carried out by playing signature calls of dolphins none of the ones in the program had met previously. Each dolphin listening to the call appeared disinterested.
However, when signature calls were played back from dolphins they had been in the company of previously, each bottlenose dolphin became excited, moved towards the microphone and ‘whistled’ in an attempt to get the dolphin to whistle back.
‘The cognitive abilities of dolphins are really well developed, and sometimes things like this are carry-along traits.
‘But to test whether this kind of social memory capacity is adaptive, we would need more demographic data from multiple populations in the wild to see if they experience 20-year separations.’
He said that the findings of advanced memory in marine mammals showed that in evolution ‘there are lots of ways to get from point A to point B.’
‘It’s nice to see this kind of ability in a non-primate, as this is a great example of convergent evolution,’ Dr Bruck adds.
His next aim is to see whether the whistles conjure up an image of the calling dolphin in the recipient’s head, as names do with humans.
He said: ‘That’s my goal – show whether the call evokes a representational mental image of that individual.’
With this new research, it looks like the old adage may need to be changed to “A dolphin never forgets”. Doesn’t quite have the same ring to it, though, does it?
On The Web:
Nice to hear you! Dolphins recognise old friends even after 20 years apart
Elephants? It’s DOLPHINS that never forget: Mammal found to recognise long-lost friends after 20 years apart