Dolphins can recognize their old tank mates’ whistles after
being separated for more than 20 years—the longest social memory ever recorded
for a non-human species.
The remarkable memory feat is another indication that
dolphins have a level of cognitive sophistication comparable to only a few
other species, including humans, chimpanzees and elephants. Dolphins’ talent
for social recognition may be even more long-lasting than facial recognition
among humans, since human faces change over time, but the signature whistle
that identifies a dolphin remains stable over many decades.