Both does and bucks snort, a sound that often signals danger.

It is used as distress code, to signal danger.

Flynn glanced around the church but neither saw nor heard anything in the shadows to signal danger.

To his most suspicious examination there was nothing to signal danger.

To signal danger, we imitated the call of the jungle owl.

The use of model or actual dead birds is used to signal danger to others.

Their large ears can move independently of each other and pick up any unusual sounds that may signal danger.

Now, just as often, it signals danger about to be increased.

Some fish may use sound to communicate with their young, and to signal danger.

What better way to signal danger, when language isn't an option?