Bullfrogs in the United States started as a way for Californians to eat more frog legs. Now, the bullfrog population grows almost completely unchecked. In many places in the world where bullfrogs have spread, there aren't predators to eat them! Readers are likely familiar with the bullfrog croak, but in this book, they'll learn why hearing it is a bad sign! The main content introduces the definition of "invasive species" and explains through the bullfrog's story the harm these animals cause. Full-color photographs help readers identity bullfrogs, and informative fact boxes add details about conservation, habitats, and food chains.