London, Jul 24 (IANS): Dolphins have long been recognised as a smart animal. A new study by British researchers has found that bottlenose dolphins address each other by using signature whistles.

Researchers at the University of St. Andrews conducted sound playback experiments with wild bottlenose dolphins on the east coast of Scotland, Xinhua reported.

Based on an earlier work that showed that dolphins often copy signature whistles of their close relatives and friends, this study tested whether animals that are addressed with copies of their signature whistles really react to them.

The researchers followed groups of wild dolphins and recorded the unique signature whistles using a novel signature identification method. They then played back either a computer version of an animal's signature whistle, or control whistles of either an unfamiliar animal or a familiar animal from the same population.

Each dolphin only reacted when hearing the computer version of its own signature whistle, but not to the other whistles played back to it.

The researchers said this showed that dolphins can be addressed in this way, and it was the missing link to demonstrate that signature whistles function as names.

"In experimental work, parrots are also good at learning novel sounds and using them to label objects," said Stephanie King, who took part in the study.

"Our results present the first case of naming in mammals, providing a clear parallel between dolphin and human communication."