The Dolphin's Whistle Rings A Bell

This is Scientific American 60-Second Science. I'm Sophie Bushwick. Got a minute?
Have you ever run into a former acquaintance and discovered that you can't remember his name?
This awkward situation is apparently alien to dolphins, who can recall old companions up to two decades later.
As a recent 60-Second Science podcast explained, dolphins have signature whistles that may serve as individual names.
But how long do they remember their friends' titles?
To find out, researchers looked at 43 captive dolphins that have moved among the same six facilities, living together in different combinations at various times.
When the scientists played unfamiliar signature whistles for each dolphin, the test subjects quickly grew bored.
But when the dolphins heard recordings of the signature whistles of former companions, they moved towards the speakers and even whistled back at them.
The study is in Proceedings of the Royal Society of London B.
Not even a separation of 20 years could dim the memory of one particular dolphin,
which suggests these mammals may have lifelong social memories.
Perhaps it's time to change the old axiom about elephants to "a dolphin never forgets."
Thanks for the minute, for Scientific American 60-Second Science. I'm Sophie Bushwick.