Dolphins communicate like humans by calling each other by "name", scientists in Fife have found.
Dolphins were monitored in Sarasota Bay off Florida (Image: Randall Wells)
The mammals are able to recognise themselves and other members of the same species as individuals with separate identities, using whistles.
St Andrews University researchers studying in Florida discovered bottlenose dolphins used names rather than sound to identify each other.
The three-year-study was funded by the Royal Society of London.
Dr Vincent Janik, of the Sea Mammal Unit at St Andrews University, said they conducted the research on wild dolphins.
He said: "We captured wild dolphins using nets when they came near the shore.
"Then in the shallow water we recorded their whistles before synthesising them on a computer so that we had a computer voice of a dolphin.
"Then we played it back to the dolphins and we found they responded. This showed us that the dolphins know each other's signature whistle instead of just the voice.
"I think it is a very exciting discovery because it means that these animals have evolved the same abilities as humans.
"Now we know they have labels for each other like we do."
The research was conducted in Sarasota Bay off Florida's west coast.
The findings are published in the US journal the Proceedings of the National Academy of Sciences (PNAS).