If you’re headed outside, some experts warn you should watch out for a new type of rattlesnake – silent ones.

It can be one of the most alarming sounds you hear if you come across it. It’s the warning from a rattlesnake, ready to bite with its toxic venom.

But some experts say the rattles are going silent.

“Less and less rattlesnakes are rattling,” explained Steve Reaves who is the owner of a rattlesnake removal service licensed through the Arizona Game and Fish Department.

Reaves feels these snakes have now started to evolve to the point they’re losing their rattle in order to survive.

“The theory is we’ve created a snake through killing the ones that do rattle, we’ve created a rattlesnake that doesn’t tend to rattle so much,” he says.

Reaves says these silent snakes could be a big danger.

While there’s disagreement about whether this is actually a trend or not, Reaves says in some parts of the country some rattlesnakes have completely lost their rattles.

And that leaves some to wonder if the only thing worse than hearing a nearby rattlesnake is not hearing it at all.