The ruins at Tikal National Park in northern Guatemala, some nearly 3,000 years old, were reopened for Mayan rituals in the late 1990s.

IN Tikal, the ancient Mayan city in northern Guatemala, dawn is not seen — it is heard. First, a roar. Then a responding roar, then another and another — not from jaguars, but from howler monkeys, proclaiming their territory. A squeaking counterpoint begins: the raccoonlike coatimundi greeting one another as they forage for food. Finally the birds join in, toucans clicking their long bills and parrots shrieking, the prima donna first violins bringing the symphony to a climax.