(Update: Big cats can protect humans from the rise of future pandemics. See more in National Geographic News.)
At dusk one evening, deep in a Costa Rican forest, a young male jaguar rises from his sleep, stretches, and silently but determinedly leaves forever the place where he was born.
There's shelter here, and plenty of brocket deer, peccaries, and agoutis for food. He has sensed, too, the presence of females with which he might mate. But there's also a mature male jaguar that claims the forest—and the females. The older cat will tolerate no rivals. The breeze-blown scent of the young male's mother, so comforting to him when he was a cub, no longer binds him to his home. So he goes.