Readers of all ages will be fascinated by the ever-changing life cycle of the arctic tundra. Learn which animals come and go and how they survive in this frozen desert. As spring approaches, the temperatures are still freezing. Thousands of caribou begin to travel north along the same paths that caribou have traveled for centuries to graze on tundra grasses. It is not until the fall "freeze-up" that the caribou begin their migration south once again...