We don’t mean to spoil the beloved movie, Jurassic Park, but this news is fascinating… and slightly disturbing. The sounds you hear when the velociraptors communicate together are actually mating tortoises.

Sound designer Gary Rydstrom received two Academy Awards for his work on Jurassic Park, one for Best Sound and the other for Best Sound Effects Editing.

He told Vulture the truth behind the voice of the Raptors:

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… 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.

But tortoises weren’t the only animals used to create the sound of the velociraptors.

The breathing noise the raptors make is actually a horse, while the hiss comes from a goose.

Birds make pretty raspy sounds, but geese are famous for being the nastiest. You’ve got to get a goose mad and then they hiss at you, and it doesn’t take much to get a goose mad because they seem to get mad at everything. All you have to do is get close to one and stick a mic near its beak and you’ll get that hiss, and that’s the hiss that Muldoon [the game warden] hears before he dies.