Three Asian elephants at the Bronx Zoo in New York City were able to distinguish themselves from others in a huge mirror and did not seem to mistake their reflection for another elephant, said the study published Monday in the Proceedings of the National Academy of Sciences.

The elephants used the mirror to inspect themselves, moving their trunks to look inside their mouths, the scientists said. And the elephants tested the mirrored images by making repetitive, rhythmic movements.

One 34-year-old elephant named Happy passed an important test of self-recognition, known as the "mark test."

Each elephant was marked with visible paint on its forehead, and Happy repeatedly touched the tip of her trunk to the mark. That response requires an understanding that the mark is not on the mirror but the elephant's body, the researchers said.

An invisible "sham" mark was also placed on each elephant, to see if the feel or smell of the mark might cause them to touch that spot. Happy only touched the visible mark with her trunk.

Only humans, great apes and bottlenose dolphins have demonstrated similar self-recognition in mirror tests, the researchers said. Other animals put through the same test have failed.

"As a result of this study, the elephant now joins a cognitive elite among animals commensurate with its well-known complex social life and high level of intelligence," said Frans de Waal, one of the authors of the study and director of Yerkes National Primate Research Center at Emory University in Atlanta, Georgia.

Elephants had failed to display self-recognition in previous research, but this time they were exposed to a larger mirror, eight feet (2.4 meters) high and eight feet wide.

"Elephants have been tested in front of mirrors before, but previous studies used relatively small mirrors kept out of the elephants' reach," said Joshua Plotnik, a researcher at the Yerkes center.

"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," he said.

The preliminary findings will be followed up by further research to explore behavioral and cognitive evolution in elephants, especially the social complexity of Asian elephants, the team said.

The study was carried by de Waal and Plotnick at the Yerkes National Primate Research Center in collaboration with researcher Diana Reiss of the Wildlife Conservation Society in New York.

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