We know what you're thinking -- it's kind of pathetic -- but consider that the other options are to either hide or hop away. Frogs have no kung-fu.
If they are picked up or cornered by a predator they will sometimes let out a high pitched ‘scream’ to try and scare they predator off. This does not necessarily mean the frog has been harmed.
Not sure how effective this tactic is. However, it's the best Cartman impression we've ever seen from an amphibian.
As a bonus, here's the screaming frog, death metal style: