It was a question in one competition, but it remained unanswered and i am curious about an answer. There was a hint: American bullfrog but i can not find any example of this behaviour on the web.
The closest I can think of with that hint is a Middle Eastern beetle that hunts frogs and other amphibians:
However, it's only a pseudo-fit to the clue. The beetle doesn't hunt American bullfrogs, but ones native to its area of the world.