What do an elephant, a mouse, and a dolphin have in common? They're all mammals! But do you know what makes a mammal a mammal? Read this book to find out! Learn all about birds, insects, reptiles, and other animal groups in the Meet the Animal Groups series - part of the Lightning Bolt Books(tm) collection. With high-energy designs, exciting photos, and fun text, Lightning Bolt Books(tm) bring nonfiction topics to life!