Speaking of rattlesnakes...

[Nutriaitch]

Rattling just means the snake feels threatened. It means "back off please!" That's why we have to watch out for them too- they don't always have a chance to react when caught off guard.

nothing scientific, just anecdotal, but allegedly snakes in Central and West Texas no longer rattle as often as a warning.
they have apparently "learned" that rattling sometimes attracts humans to kill them rather than avoid them, so that warning rattle is no longer a sure thing.

no clue if that's true, or just rumors that are floating around the area now.