Rattlesnake's warning changes.

[Tugaloo]

We have seen some Timber Rattlers and Eastern Diamondback rattlesnakes as we keep our distance, we've never heard them rattle.
When I was searching for rattlesnake information in Georgia. Although it wasn't what I expected; as it explained the reasons for "Don't Tread on Me"; I found it very interesting.

The Rattlesnake as a Symbol of America - by Benjamin Franklin
http://www.greatseal.com/symbols/rattlesnake.html

[RICHFL]

I hear that rattle I move back and don't look back jack....!

[Tugaloo]

When you hear the sound of a rattlesnake's rattling change from slow to fast; you're getting closer.

https://www.cell.com/current-biology...822(21)00973-8