For those of you that think rattlesnakes only attack when provoked, you are sadly mistaken. They kill numerous amounts of livestock and pets every year. They are one of the most dangerous creatures in the area. They are one of the main reasons I carry a gun when I go hiking, besides rednecks and perverts.
Rattlesnakes only bite if provoked. That is basically the only reason why they have venom. So if your dog is romping around the desert or prairies eating everything that moves, if they are biten by a rattlesnake then it is their own fault and not the snakes.