Dolphins can remember their friends for decades.

Elephants aren’t the only animals with impressive memories — dolphins have the longest social memory of any nonhuman species and can remember their friends for more than 20 years. They don’t do so by sight, however; these highly intelligent mammals actually recognize each other’s whistles, even after being separated from one another for more than two decades. 

This discovery was made by a Royal Society study that collected data from 53 bottlenose dolphins at six different facilities. Whether in Chicago or Bermuda, their findings were consistent: Dolphins really do remember their besties. They have signature whistles that essentially function as names to which they’ll respond when called, something they often do in group settings to help distinguish themselves from the rest of their pod.