Calakmul is part of what remains of the huge tropical forest north of Panama, from south of Cancún in the states of Quintana Roo and Campeche to Belize and northeastern Guatemala. The region is known asthe Mayan jungle and covers more than two million hectares. The tropical climate produces an average annual temperature of 250C, from 1,000 to 1,500 mm of rain a year, and a clearly defined rainy season between June and November. The combination of inaccessibility, the lack of a permanent water supply, and the existence of illnesses such as malaria accounts for the survival of this immense jungle and its species' relative protection during the last two decades of activities by loggers, rubber tappers and hunters.

3:30 am

At three-thirty in the morning, just when I am getting back to sleep, our assistant comes to wake me. I leave the tent, wondering at the clear sky and its innumerable stars and carrying my knapsack with my binoculars, cameras, my global positioning system, a bottle of water and some pieces of candy. The other members of the group include the guides, Pancho Zavala and Javier Díaz; a doctoral student, Cuauhtémoc Chávez; an expert jaguar trapper,