Secret of 'Jurassic Park' raptor sounds? Tortoise sex

If you're a fan of all things dinosaur, especially from the Steven Spielberg's 1993 classic "Jurassic Park," you probably already know that the sound design in the movie wasn't easy.

Gary Rydstrom, a Lucasfilm sound designer and now director of the new George Lucas movie " Strange Magic," was tasked with creating dozens of dinosaur sounds from scratch using animal noises.

The vocalizations of the velociraptors in "Jurassic Park" weren't the recordings of angry animals, Rydstrom told Vulture in 2013, but in fact rather less intimidating reptiles getting it on.

"It's somewhat embarrassing, but when the raptors bark at each other to communicate, it's a tortoise having sex," Rydstrom said. "It's a mating tortoise! I recorded that at Marine World...the people there said, 'Would you like to record these two tortoises that are mating?' It sounded like a joke, because tortoises mating can take a long time. You've got to have plenty of time to sit around and watch and record them."

Various other raptor noises in the movie were in fact recordings of horses breathing and annoyed geese.

So when Rydstrom was making the rounds again this week for press junkets promoting his latest film, "Strange Magic," SF Gate's pop-culture critic Peter Hartlaub asked again about the tale of tortoise sex in "Jurassic Park," seeing as how we're getting another installment in the dinosaur action series with " Jurassic World" -- due to hit theaters in June.

"The bark that (the velociraptor) makes. When it comes in the kitchen and it barks. 'Arp! Arp!' That's the sound of a tortoise that is mating," Rydstrom told SF Gate. "The male tortoise would go up, and then fall off, and then go back again. It's riding on the back of the female tortoise. So it's climbing up her shell basically, and then it falls off. It's a little sexual."

Since raptors will be returning in "Jurassic World," we can't wait to hear more tortoises making the beast with two shells.