Whales are known for their impressive communications skills which allow pods to 'talk' to each other through complex clicks and singing, even when they are 100 miles apart.
But a new experiment has shown the mammals are also apparently capable of mimicking human speech, a feat that was previously believed to be limited to primates, birds, elephants, dolphins and seals, the Daily Telegraph reports.
Scientists say they have recorded a killer whale named Wikie repeating the words 'hello' and 'bye bye', counting up to three, and even saying the name of her trainer 'Amy.'
The 14-year-old orca lives in Marineland at Antibes, France, and is the first in the world ever recorded by scientists allegedly saying human words.
The achievement is even more remarkable because whales do not have the same vocal ability as humans having evolved to make their own sounds underwater. While humans use the larynx to speak, whales produce sounds through their nasal passages using bursts of air.
Recently scientists have discovered that whales have different 'accents' or 'cultures' and the new study suggests that those differences are picked up when young through imitation of adults, in a similar way to how children learn to speak through copying.
Writing in Proceedings of the Royal Society B, José Abramson of the Complutense University of Madrid, said: "Vocal imitation is a hallmark of human spoken language, which, along with other advanced cognitive skills, has fuelled the evolution of human culture.
"We found that the subject made recognizable copies of all familiar and novel and human sounds tested and did so relatively quickly, most during the first 10 trials and three in the first attempt.
"Our results lend support to the hypothesis that the vocal variants observed in natural populations of this species can be socially learned by imitation."
In the wild, killer whales live in pods and each has its own dialect, which includes calls that are completely unique to themselves. Some clicks are even thought to represent names. But it was unclear where that knowledge came from.
Previously killer whales have been observed mimicking the barks of sea lions and the whistles of sea dolphins and beluga whales have been filmed apparently imitating humans, but until now no controlled experiments have been carried out to verify the reports.
In the new trial, Wikie was trained to understand a 'copy' signal then invited to repeat 11 completely new sounds given by her trainer. They included words and also noises such as an elephant call, a wolf howl and a creaking door.
Wikie was given a fish or an affectionate pat when she achieved the sound to reinforce the learning. Six judges were then asked to rate whether the vocalisation matched the original word or noise.
The researchers concluded: "In sum, Wikie made recognizable copies of the demonstrated sound judged in real time by two observers, Wikie's trainer and one experimenter, later confirmed by both after listening to the recordings.
"The subject's matching accuracy is all the more remarkable as she was able to accomplish it in response to sounds presented in-air and not in-water, the species' usual medium for acoustic communication.
"It is conceivable that our data represent a conservative estimate of the killer whale's capacity for vocal imitation."
The whale words were also analysed in waveform and matched the human words when the acoustical recordings were compared.