Ghidorah's Tails: What Are They Used For?

I've noticed that nobody has really covered this detail, probably because it's very minor. But during the IMAX trailer, when Godzilla and Ghidorah are facing off, it cuts to Ghidorah, who then lightly roars at Godzilla. During that scene, if you look and listen very closely, you can hear a rattling sound, similar to a rattlesnake when threatened, and actually see Ghidorah shaking his tails. Also, when we first see Ghidorah, we see his tail, with his tail spikes proceeding to open up, making a slight rattling sound in the process. So, what's the significance of this? Simple: Ghidorah is trying to intimidate Godzilla. He does this as a way to say, "Don't mess with me, I'm bigger and stronger than you." This is just a minor but unique detail that they added to Ghidorah, especially since his movements are similar to that of a Cobra when it's about to strike. Let me know what you think about this, and if you think that it's a cool detail or not.