When it was time to turn in, I noticed that Rocky had rolled out a pad nearby but was sleeping right out on the sand, and pretty near the water.

“Aren’t you worried about bugs and critters?” I asked him through the jungle night.

“No, I like sleeping out. I mean, there are crocodiles and jaguars around, but they usually don’t bother you. And there are also vampire bats,” Rocky added calmly.

“What? Really?” I asked, fumbling with the zipper to my tent.

“Yes. They are nocturnal and feed exclusively on blood. They fly out at night to feed and drink about half their body weight in blood. When they reach their prey, which are usually sleeping, they use their razor-sharp teeth to puncture the skin. Most people think they suck blood, but they really lap it up as it oozes out.”

I found the zipper and closed the tent door a little quicker than I usually would.

“They have plenty of other mammals around to feed on, so they rarely bother humans,” Rocky added as I checked all the inside corners of my tent for holes. Then I settled in for a fitful sleep, filled with images of silent, furry, fanged creatures with huge, wide eyes winging silently through the jet-black night.

14

The next day, we stopped along the river and explored the pre-Columbian Mayan ruins of Yaxchilan and Piedras Negras, which sat on the banks of the Usu and had been inhabited in the seventh century B.C. Yaxchilan had been fairly well excavated, but Piedras Negras was like walking into an Indiana Jones adventure. The plazas, temples, and palaces, all constructed of limestone, had been only partially exposed by archaeologists, while most of this ancient ruin remained choked with thick jungle vines and vegetation.

We climbed the steep rock stairs to the tops of sacred pyramids once used for human ritual sacrifice and touched the carved depictions of ancient rulers. We found a sundial, still faintly visible despite the ravages of time. It was unnerving and exhilarating to explore the remains of this ancient world, shadowed by giant ceiba trees, crumbling back into the jungle, forgotten by the modern world.

Back in our kayaks, not far downstream, we came to an amazing natural wonder called Cascada Busilja. Here, a tributary entered the Usumacinta and announced its arrival with a spectacular fifty-five-foot waterfall.

The force of this cascade shoved us back as we tried paddling over to the bottom. What sounded like a thousand showerheads engulfed my ears and water hammered me in the face. Rob noticed that there were actually two waterfalls, one on top of the other, with a big pool between them.

“From a ways off,” he said, “they look like big knuckles, with foamy white spray cascading down over them.”