Although it's been said that elephants never forget, it now appears that dolphins may have them beat in the memory department.
Even after being separated for more than 20 years, dolphins can recognise former tank mates' whistles, new research shows.
The study demonstrates the longest social memory ever recorded for a nonhuman species. Dolphins' long-term memory for other dolphins' whistles may be even more long-lasting than humans' ability to remember other people's faces, the report suggested. Previous research has shown that each dolphin has its own unique "signature" whistle that appears to function as a name.
How the research was done
The new study, published in the Proceedings of the Royal Society of London B, included 53 bottlenose dolphins at six facilities that are part of a breeding consortium that has rotated dolphins between sites for decades, and kept records on which ones lived together.
When hearing recordings of individual signature whistles, the dolphins had much stronger responses to the whistles of dolphins they once knew - even if it was decades ago - than to whistles of unfamiliar dolphins, according to the findings.
"This shows us an animal operating cognitively at a level that's very consistent with human social memory," said study author Jason Bruck, who conducted the study while working on his Ph.D. at the University of Chicago's program in Comparative Human Development.
However, it's not clear what signature whistles signify in a dolphin's mind.
"We know they use these signatures like names, but we don't know if the name stands for something in their minds the way a person's name does for us," Bruck said. "We don't know yet if the name makes a dolphin picture another dolphin in its head."
He'll attempt to get answers to that question in his next round of research.
For this round, he used data from dolphins at six facilities, including Brookfield Zoo near Chicago and Dolphin Quest in Bermuda.
"This is the kind of study you can only do with captive groups when you know how long the animals have been apart," Bruck said. "To do a similar study in the wild would be almost impossible."
Earthtrust has more about dolphins.
Image of dolphins from Shutterstock.