In Star Trek IV: The Voyage Home, an alien species threatens to destroy the Earth after humpback whale songs go quiet. But planet-destroying extraterrestrials might not be the only intelligent nonhuman species listening to whales.

Bottlenose dolphins at the Planète Sauvage aquarium in Port-Saint-Père, France, sound like they are mimicking recorded humpback whale songs, reported Science.

If immersion is the best way to learn a language, the dolphins have their work cut out for them. Whale songs, seagull calls, music and other sounds play over loudspeakers in the park as the dolphins perform. But underwater microphones recorded the studious cetaceans working overtime, practicing at night what sounds like humpback vocabulary lessons.

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Researchers discovered the dolphin's nocturnal practice sessions by accident. Martine Hausberger of the University of Rennes 1 and her colleagues wanted to know more about the sounds dolphins make at night, so they hung underwater microphones in the performing dolphins' tank overnight.

The recordings held 25 whale-like sounds never heard from these dolphins before. The researchers used a computer program to match the dolphins' sounds to humpback whale calls. The scientists also played the dolphins' whale-like vocalizations to 20 human volunteers. Humans incorrectly identified the dolphins' vocalizations as whale songs approximately 76 percent of the time.

The research was published in Frontiers in Comparative Psychology.

The dolphins observed in this study lived in captivity their whole lives and had never heard a real whale. Hausberger believes they picked up the whale songs during their performances because showtime heightens the dolphins' focus.

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If further research proves that the dolphins are indeed mimicking the whales, it will be the first time dolphins have been observed to hear a sound, then mimic it hours later. Hausberger hopes to monitor the dolphins' brains to determine if they are sleeping while making the whale calls, which could suggest dolphins process new information while they sleep.

To decide for yourself if the dolphins are passing Whale 101, listen to the recordings on Science's website: Do Dolphins Speak Whale in Their Sleep?

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IMAGE: A female bottlenose dolphin at the U.S Navy's Marine Mammal Research Program. (Credit: Jessica B. Davis, Wikimedia Commons).