WASHINGTON In a reflection of their intelligence, bottlenose dolphins named Presley and Tab at the New York aquarium have displayed the ability to recognize themselves in a mirror -- a quality previously seen only in people and the great apes, researchers said on Monday. According to Reuters, the two male dolphins were housed in a pool with reflective glass walls at the aquarium in Brooklyn. researchers found the dolphins reacted to their own reflections without the social responses they displayed when seeing other dolphins. Testing whether they could distinguish themselves from other dolphins, the researchers placed markings in non-toxic black ink on various places on the bodies of 13-year-old Presley and 17-year-old Tab. The dolphins then swam to the mirror walls and exposed the mark to the reflective surface in order to look at it. The location where they were marked changed from session to session -- sometimes, for example, between the pectoral fins, on the tummy, or on different parts of the head. The dolphins were indifferent toward the markings on one another. But they swam more quickly to the mirror after a black mark had been left on their bodies, the researchers found. They spent more time in front of the mirror after being marked than when they were not marked, and the first behavior when arriving at the mirror was exposing the black mark to check it out. "One of the things we try to do is find ways of characterizing and measuring and comparing intelligence in other animals across species," Diana Reiss, a scientist in the Wildlife Conservation Society's Osborn Laboratories of Marine Science located at the aquarium, said in an interview. "So this is one of those nice studies that allows us to say these abilities are not just found in primates, they are also seen in dolphins. It lets us really get a better understanding of the nature of the dolphins' intelligence." Reiss conducted the study with Lori Marino of Emory University in Atlanta. "There are places in the world where these animals are being slaughtered," Reiss said. "This perhaps may heighten our awareness of the importance of conservation efforts and the need to protect these animals."