Elephants have been found to recognise themselves in a mirror, putting them in an exclusive club of self-awareness whose other members are great apes (including humans) and bottlenose dolphins.

"The social complexity of the elephant, its well-known altruistic behaviour and, of course, its huge brain, made the elephant a logical candidate species for testing in front of a mirror," said Joshua Plotnik, a psychologist at Emory University in Atlanta, who led a team whose study was published yesterday in the Proceedings of the National Academy of Sciences.

An 8ft mirror was put in the elephant enclosure at the Bronx zoo in New York and a watch kept on its three inhabitants. The first question was if they greeted their reflection as if meeting another individual - they did not make this mistake, and used the mirror to inspect themselves, for example, moving their trunks to look at the inside of their mouths.

"Elephants have been tested in front of mirrors before, but previous studies used relatively small mirrors kept out of the elephants' reach," Dr Plotnik said. "This study is the first to test the animals in front of a huge mirror they could touch, rub against, and try to look behind."

Inspecting the mirror and trying to look behind it - as did the Bronx elephants - is another indicator of self-awareness. One of the three also passed the "mark" test when painted in a place it would normally be unable to see. It touched the paint mark on its head after looking in the mirror.

Diana Reiss of Columbia University in New York said that the research helped explain the society in which elephants lived: "Humans, great apes, dolphins and elephants, well known for their superior intelligence and complex social systems, are thought to possess the highest forms of empathy and altruism in the animal kingdom."