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Constant squeaking by baby bats bears is very similar to human infants learning to talk!

That's according to scientists who've been listening in on bat roosts in Costa Rica.

They've discovered that the bats produce rhythmic sounds and repeat key "building block syllables" which suggests their babbling is the beginning of bat communication - just like children learning to talk!

"They just babble away, sunrise to sunset, practising their sounds," lead researcher Dr Ahana Fernandez said.

Dr Fernandez, based at the Museum of Natural History in Berlin, studied a particularly chatty species - the greater sac-winged bat, Saccopteryx bilineata.

"These bats actually sing like songbirds," she said

Dr Fernandez and her colleagues, who published their findings in the journal Science, studied recordings of the bat pups babbling in their roosts.

Human speech requires very precise control over the voice and babbling in infants and toddlers is vital practice in gaining that control. And, the researchers said, the same was true of bats.

"We know all the different syllable types produced by adult bats," Dr Fernandez said. "And the ones that appear in pup babbling are really reminiscent of the adult ones - so we can clearly tell."

The greater sac-winged bat is the only bat species known to do this so far.

But with more than 1,400 bat species in the world, Dr Fernandez "really thinks there will be another that babbles".

'Really listening'

And while this study has identified a pattern that could be important for many mammals that have to learn to communicate vocally, she also says there is a great deal left to understand about this specific species of singing bat.

"The babies really listen to each other when they're babbling," Dr Fernandez said.

"One starts, he babbles for 15 minutes or so, and I can clearly see the ears of the other pups moving.

"So I think they're really listening to each other - but how it influences their practising, I don't know."