Millions of years ago, before man, before the ice ages, when the world was warm and humid, forests like these covered much of the earth. And it was here, rough eons of geological time, that a profusion of life evolved. The remnants of those primordial jungles are the rain forests of today. They are home to half of all the animal species on earth. Yet, in the shady depths of the forest, there is seldom more than a fleeting glimpse of this abundance. When they are seen, the animals are often revealed as strange and splendid examples of natural perfection and adaptation. Myriad in their diversity and sometimes bizarre in form, these creatures give the somber forest a special mystery and splendor. Endless rains and high temperatures create the steamy atmosphere in which rain forests thrive. These conditions occur now only in a narrow belt around the equator where forests blanket some three million square miles of the earth's tropics. Within this belt lies the small Central American country of Costa Rica, which possesses one of the richest natural endowments on earth. When Christopher Columbus landed here in 1502, he found a mountainous land of rivers and forests like those he'd seen ten years earlier in Hispaniola.