I knew at once what it was — a garter snake had caught a wood frog. I followed the sound to its source, where I discovered a three-inch frog halfway down the throat of a two-foot-long garter snake.

In Três Pontas, Brazil, a small snake slithered too close to the wrong predator. A motionless and watchful frog suddenly lunged—grabbing the snake and swallowing it whole. The filmer ...