WASHINGTON (AP) — Forget elephants. Dolphins can swim circles around them when it comes to long-term memory.

Scientists in a new study repeatedly found that dolphins can remember the distinctive whistle made by another dolphin they haven't seen in two decades. The whistle acts as a name to the marine mammal.

A dolphin named Bailey hadn't seen another dolphin named Allie since the two juveniles lived together at the Dolphin Connection in the Florida Keys. Allie ended up in a Chicago area zoo, while Bailey got moved to Bermuda. Yet 20 1/2 years later, Bailey recognized and reacted to Allie's distinctive signal when a University of Chicago researcher played it on a speaker.

Other dolphins had similar steel-trap memories.

The study is in Wednesday's Proceedings of the Royal Society B.