When it comes to long-term memory, dolphins far outnumber elephants . A study from the University of Chicago (USA) published in the Proceedings of the Royal Society B concludes that these aquatic mammals have the longest social memory ever recorded in animal species. Specifically, working with 53 specimens of bottlenose dolphins ( Tursiups truncatus ), Jason Bruck and his colleagues have shown that they are capable of remembering and recognizing the characteristic whistle of another dolphin with which they have lived after more than 20 years without hearing it. And that is important considering that recent research reveals that each dolphin develops a unique and characteristic hiss that functions as a name that allows others to identify them.
Why the social memory of dolphins is so persistent is, at the moment, a mystery. Dolphins display sophisticated social connections that follow a "fission-fusion" pattern , such that in the open ocean they can separate from one group and join the members of others many times. These kinds of relationships might have required an increase in your memory capacity. Although it is also possible that this brain capacity has a totally different origin. In any case, Bruck assures that "it is pleasant to observe these abilities in non-primates, because it constitutes an important example of convergent evolution".
