Study finds dolphins have longest social memories among animals

Bottlenose dolphins can remember each other's signature whistles for more than 20 years, a study finds, the longest social memory observed in an animal.

Elephants have long been credited with the animal kingdom's most prodigious memory, but evidence for that was anecdotal, said the study's author, Jason Bruck of the University of Chicago's Institute for Mind and Biology.

Bruck claims to have compiled the first study showing social recognition in an animal persisting beyond two decades - possibly "the longest pure memory of any kind in a non-human species".

For the study published in the Proceedings of the Royal Society B: Biological Sciences, Bruck worked with 43 captive dolphins at six zoos and aquariums in the US and Bermuda, collecting whistle recordings he played to them over underwater speakers.

This comes on the heels of research at the University of St Andrews in Scotland, which shows that dolphins design unique signature whistles as "names" to identify themselves, and answer when called by their "names".

They use these whistles like we identify people by their faces.

Bruck played dolphins the recordings of signature whistles from those they had once shared a tank with, as well as the calls of complete strangers.