Growling, squawking, chirping and purring fill the air—but do you know what it all means?

Many animals use sound to communicate. Just like people, the sounds they make can tell others when they are happy, scared, angry, or playful. You probably know the difference between a cat's angry hiss and contented purr. A dog's bark lets everyone know it's on the alert. But what about lions, grasshoppers, and fish? Can you speak alligator?