Discover Mammals in this Beginning Reader They're furry! They have cute babies! They're mammals! Beginning readers will learn all about mammals in this short, leveled reader. Here is an example of the text level: All mammals are warm-blooded. That means the temperature of their blood stays about the same, even if it is a hot day or it is snowing outside. This elk keeps his blood the same temperature even when it is below freezing outside. Discover Reading series books from Xist Publishing are created with digital and print reading in mind. Each page features a photograph with descriptive text leveled for early readers.