Belugas can even mimic human speech

Some toothed whales absorb vocalizations exceptionally well, which helps them develop into outstanding mimics. For example, bottlenose dolphins and orcas have been found to coexist and bottlenose dolphins have even been observed to mimic humpback whale sounds. However, belugas are extremely skilled impersonators and have even shown signs of being able to imitate human speech. Researchers have documented instances of wild belugas producing noises resembling "a mob of youngsters shrieking in the distance," for instance, while some captive belugas have even been heard speaking in human tones, a real human may have been duped at least once.

Beluga whales kept in captivity are rumored to mimic their human caretakers' speech. One of the first belugas to be seen acting in this way was a whale by the name of NOC, who lived 30 years at the National Marine Mammal Foundation in San Diego. A human diver was once persuaded to exit the whale's tank after hearing what he believed to be another person telling him to do so. It was discovered that NOC had made the noise by imitating the word "out." A diver came to the surface from a tank containing NOC and questioned, "Who told me to get out?" The diver was reacting to a "command" from NOC himself, researchers would later write in Current Biology. The juvenile male beluga has learned to make extraordinarily low-frequency noises, sometimes loud enough to seem like words, with an amplitude and frequency (200 to 300 Hz) close to human speech. The researchers observed that NOC ceased mimicking people after he matured, although continuing to remain highly vocal as an adult.