A captive beluga whale has done something amazing: she has seemingly "learned" another language and adopted it over her own.

The whale, then four years old, started making whistling sounds unique to dolphins and dropping her own beluga vocalisations after being housed with bottlenose dolphins for only two months.

Before being moved to the Dolphinarium Koktebel in Crimea in 2013, the whale in question was well socialised with other beluga whales in her previous facility.

But after the move to Koktebel, her new companions were only bottlenose dolphins. Initially, things were awkward.

"The first appearance of the beluga in the dolphinarium caused a fright in the dolphins," write researchers Elena Panova and Alexandr Agafonov of the Russian Academy of Sciences in Moscow.

Thankfully it wasn't long before she settled in - and started copying the whistles of the dolphins. In turn, she gradually stopped making beluga sounds.

The team recorded over 90 hours of audio. In the first fews days in the dolphinarium, the whale made sounds typical for her species. Two months later, she was "speaking dolphin."

What's particularly interesting is that she started making the dolphins' signature whistles -individual whistles assigned to each dolphin, sort of like names. And she stopped using the beluga contact call, which beluga whales use as a sort of call-and-response check-in.

A year after her introduction to her new dolphin roomies, the proportion of her calls that were similar to dolphin sounds was no different from the recordings at the two-month mark. She'd seemingly created her own cetacean pidgin.

And the learning was not a two-way street.

"The inspection of the audio recordings made before and after the beluga's introduction revealed that the cross-species imitation was not reciprocal," the researchers wrote.

"While the imitations of dolphin whistles were regularly detected among the beluga's vocalisations, we found only one case in which the dolphins produced short calls that resembled (but were not identical in physical parameters) those of the beluga."

This, they note, was probably due to the differing social conditions of the two species. The beluga, a social animal, was the only one of her kind present, and therefore had to adapt to fit in.

It's well documented that beluga whales are powerful mimics. They have been observed making human-like sounds, as in the case of Noc, a beluga whale studied by the US Navy in the 1970s, seen in the video below. More recent experiments have shown that they can even be taught to mimic computer-generated artificial sounds.

But therein lies a large rub: while there's no doubt the beluga whale was mimicking dolphin sounds, it's unknown whether she understands dolphin "language" or has just picked up some new sounds.

Even if she doesn't understand what her sounds mean, there's an important social benefit for the beluga whale to learning the local lingo.

"The case reported here, as well as other instances of imitation and whistle sharing in dolphins described in the literature, may be considered as vocal convergence between socially bonded individuals - a phenomenon that can be seen in various vocal species, from birds to humans," the researchers wrote.

"With some exceptions, call convergence is suggested to provide recognition of a group and strengthening of social bonds between its members."

More research could help determine whether and how much she understands, and whether this is a unique case of complex interspecies communication.

The research has been published in the journal Animal Cognition.