From the top of Shifting Sands dune in the Serengeti Plain of Africa a million mammals are in motion. Wildebeests. Zebras. Gazelles. The plain is black with them. It is wildebeest calving season, and many of those giant bearded antelope have newborns trailing them. Others walk with the distended bellies of imminent birth. From a distance the movement seems a serene and constant march toward the southeast, where recent rains have made pastures greener. But a closer look reveals details of high drama.

A young Grant's gazelle suddenly dashes between the clusters of wildebeests, followed closely by its mother. A hyena races in pursuit. The mother slows and moves evasively to distract the hungry predator. But the inexperienced fawn makes a