Director Steven Spielberg used recordings of tortoises having sex to come up with the unique dinosaur sounds featured in his adventure epic Jurassic Park.

Oscar-winning sound engineer Gary Rydstrom was tapped by Spielberg to create dozens of distinct noises for the blockbuster, and he travelled around the world collecting sounds from various animals for inspiration.

Rydstrom tells New York Magazine, "If people knew where the sounds in Jurassic Park came from, it'd be rated R! It's somewhat embarrassing, but when the raptors bark at each other to communicate, it's a tortoise having sex. It's a mating tortoise! I recorded that at Marine World (in California)."

The 53-year-old sound guru also incorporated geese, donkeys and elephants in the 1993 hit — and even horses and dolphins in heat.

He adds, "I remember recording a female horse, and the male horse came right by her and she squealed because she was in heat ... And that's the squeal the Gallimimuses (dinosaurs) make ... (And) one of the key elements of the raptor screams was a boy dolphin in heat, so you can see a pattern here!"