Allie and Bailey knew each other when they both lived in Florida. More than 20 years later, Allie lives near Chicago and Bailey lives in Bermuda, but Allie’s name still rings a bell for Bailey. That would not be breaking news, except that Allie and Bailey are not people: they are dolphins.
Bailey’s recollection of Allie’s name — or more precisely, of her 'signature whistle', which functions as a name among dolphins — is the most durable social memory ever recorded for a non-human. Yet it is only one of many data points in a study that found that it is the rule, not the exception, for bottlenose dolphins (Tursiops truncatus) to recognize whistles from their distant past. “We can’t tell yet what the upper limit is time-wise, or even if there is one,” says Jason Bruck, a biologist at the University of Chicago who published the results today in Proceedings of the Royal Society B. “We just know it’s at least 20 years.”
Via Dr. Stefan Gruenwald