My experience is that rattlers won’t buzz unless you stay too near to them for long enough that they become threatened. Most people bit by a rattlesnake never heard them buzz. I had a baby in my backyard that didn’t even make a sound before he got whomped with a rake.
Of course, this hog story does seem to make a good excuse for blasting some feral hogs.
Nueces Helicopter Pig Hunt (no music)
http://www.youtube.com/watch?v=xiHmYsyVniE
“This feral hog eradication program is funded by a group of farmers who are taking progressive action to reduce the devastation done to their crops by these animals. Each and every feral hog is estimated to cause $1400 in crop damage during its lifetime. As you can see this data in combination with the extraordinarily high and ever expanding hog population proves to be a very big problem.”