They don't always rattle, but when they do they are going to be aggressive. It's different, say, when they're hunting, but hunting is an act of aggression in its own right.

The analogy works, because of the visual, because of the poison (potential to harm), and because everyone knows rattlensnakes are dangerous. They're iconic, in a sense.

I'm not sure everyone around the world knows off that bat that a Copperhead or a Water Moccasin is poisonous.

Water Moccasins have a teigger warning too, but it's visual so lots of times you miss it, if you didn't know the snake was already there. They'll flash cotton mouth.

Rattles and cotton mouths aren't much of a useful warnint though, because they usually happen right before the strike. You don't have much opportunity to respond, depending. on proximity. With Copperheads, you rarely ever see them. Spotting them is a skill set by itself. I think I've seen less than 20 and I've spent a lot of time out in the woods.

But yeah, during the hot summer months they're just damned irritable. Everyone says so.