DOLPHINS can recognise a familiar whistle even after more than 20 years apart, research has shown.
This is the longest social memory ever recorded outside humans, and is found in only a few other species such as elephants and chimpanzees.
The researchers say that dolphins’ abilities may even beat humans in this respect, given that human faces will change over time but dolphins’ signature whistles stay the same.
In tests where researchers played dolphins recordings of other dolphin’s whistles, the dolphins responded by swimming towards the speaker and even whistled back when they heard a familiar whistle.
However, when being played whistles from unfamiliar dolphins, they quickly became bored, showing that they were really responding to recognition only.
“This shows us an animal operating cognitively at a level that’s very consistent with human social memory,” said Dr Jason Bruck, who conducted the study whilst at the University of Chicago.
The study was carried out on 53 different captive bottlenose dolphins, used because there were long records of where each dolphin had been throughout its life and therefore which other dolphins it had been in contact with.
This follows on from the recent research from scientists at the University of St Andrews that showed each dolphin has a unique whistle that acts like a name.
Researchers are now intrigued as to how and why dolphins have developed such an impressive memory, as there doesn’t seem to be an evolutionary need for it.
“The cognitive abilities of dolphins are really well developed, and sometimes things like this are carry-along traits,” said Bruck.
Bruck’s next goal is to find out how similar dolphins’ names are to human names, to test what dolphins’ think of when they hear the whistles.
“We know they use these signatures like names, but we don’t know if the name stands for something in their minds the way a person’s name does for us,” Bruck said. “We don’t know yet if the name makes a dolphin picture another dolphin in its head.”