The latest King Kong movie, Kong: Skull Island, is set in an uncharted island in the Pacific Ocean where prehistoric animals have gotten very big — and loud. Aside from a giant ape that walks like a man, we have enormous ants that chirp like birds, and gigantic roaring lizards. The way these monsters look is often based on real animals. But what about the sounds they make? Are those accurate?

We wanted to look into what a giant beast should sound like — whether it’s Godzilla, the prehistoric Kong lizards, or more realistic dinosaurs. So we asked paleontologists, who’ve been trying to figure out what dinosaurs sounded like for decades. It’s hard to get an answer because the vocal organs used to make sounds, like the vocal cords in our throat, are mostly made of flesh. And flesh doesn’t fossilize.

But still, scientists can look at dinos’ modern-day relatives — like birds and crocodiles — and make some educated guesses. Watch the video above to find out more, but first off, one big disclaimer: movie monsters are obviously imaginary creatures. So even though most lizards in real life are basically silent (unless they’re geckos), the giant lizards in Kong: Skull Island have every right to roar.

“We’re not making documentaries,” says Stuart Sumida, a paleontologist and animal anatomy specialist who advised the Kong: Skull Island filmmakers on how the prehistoric lizards should move. “People can quibble all they want about the biology of the creatures. We also know that mice don’t talk, yet we go see movies with mice that talk.”