Just imagine the fear that the dinosaurs would present to the little animals! They were so afraid that they began to look for places to live where they would be safe from the dinosaurs. Do you remember about the ice age we talked about earlier? These small animals fled to where it was colder to places where enormous reptiles could not live. As time went on, the animals that lived on the fringes of the glaciers started to grow hair or fur to protect them from the cold and kept their blood warm. These first birds and mammals were the mark of the beginning of the Cretaceous Period.