Recognising the voice of a childhood friend after more than 20 years would be a feat for most people.But Bailey the dolphin at Dolphin Quest Bermuda was able to accomplish just that during a recent research project.Dolphin Quest general manager Christine Mihelcic said yesterday: “We always want to say how intelligent these animals are, so it’s really interesting to watch them do this type of research to prove that.”As a juvenile, Bailey lived at Dolphin Connection in the Florida Keys together with another juvenile dolphin named Allie.Around 20 years and six months ago, the two animals were separated. At that time, Bailey was four years old and Allie was two.While Bailey, now 24-years-old, has lived at Dolphin Quest Bermuda since 1996, Allie now resides at the Brookfield Zoo in Chicago.During a recent study, researcher Jason Bruck of the University of Chicago visited a total of 53 bottlenose dolphins at six marine mammal parks and aquariums, including Bailey and Allie.He recorded the dolphins’ whistles and then played them to each other, along with those of dolphins they had not met, and recorded their reactions.The result of the findings, recently published in the Proceedings of The Royal Society B, was that dolphins showed significantly higher response scores to dolphins that they knew, regardless of how long they were apart. According to Dr Bruck, the results mark the longest pure memory of any kind in a non-human species.“I predicted that given the highly social nature of bottlenose dolphins, long term social recognition would not only be present, but also persistent,” he wrote in his report.“The results have matched this expectation, as I have shown that dolphins were capable of remembering each other’s whistles for 15 or more years (up to 20) with no decay. Duration of association did not affect recognition, meaning long periods of association were not required for long-term recognition.”He said that such a study would be almost impossible to be done in the wild, saying: “This is the kind of study you can only do with dolphins in human-care where you know how long the animals have been apart.”Ms Mihelcic said the research project is just one of several that Dolphin Quest Bermuda has been involved in over the years.“Because this is a seasonal location, we can focus more on research and educational opportunities during the winter months,” she said. “In addition to inspiring people to be passionate about dolphins and the oceans, our mission at Dolphin Quest is also to support vital marine education and research initiatives like this incredible project.”