A bottlenose dolphin leaps in the North Sea. Vincent M. Janik/University of St Andrews.

In the animal kingdom, bottlenose dolphins have beat elephants to clinch the honor of being the animal with the longest memory.

A new study, published in the Proceedings of the Royal Society B, showed that dolphins can remember the distinct whistle of another dolphin -- that acts like a unique signature similar to a human's name -- even after more than 20 years of separation.

Elephants, on the other hand, have a memory span of only about 10 years.

The study was conducted by Jason Bruck, a University of Chicago researcher, who told AP that he analyzed the memory power of dolphins by conducting an experiment with two dolphins -- Bailey and Allie -- who lived together at the Dolphin Connection, an organization working toward conservation of marine mammals in the Florida Keys, as juveniles.

Although the two dolphins were moved to different locations -- Allie to a Chicago area zoo and Bailey to Bermuda -- Bailey recognized Allie’s distinctive whistle after more than two decades when Bruck played it on a speaker.

"It's mind-blowing; I know I can't do it," Bruck told AP, adding that male dolphins had better memory than females. "Dolphins in fact have the longest social memory in all of the animal kingdom because their signature whistle doesn't change."

During his research, Bruck found that dolphins do not respond to whistles they don’t recognize. But if it is a whistle they recognize, “they will hover around it, whistle at it, seemingly try to get a response,” he told Science journal.

According to AP, Bruck is planning to take the research further to analyze how dolphins visualize their buddies after long years of separation.

"The study raises some very interesting questions and hints at the wider importance of long-term social memory in nonhuman mammals and suggests there are strong parallels between dolphin and human social recognition," Stephanie King, who studies dolphins at the University of St. Andrews in Scotland told Associated Press.