A downpour during the night had turned the greenish water of Río Quendeque angry and red with fresh mud, and the clouds looked ready to burst again any moment. Thankfully, we had the good boat, the one with the “roof”—an awning where giant Amazonian spiders and iridescent beetles were hanging out. I was on patrol with rangers from Madidi National Park in Bolivia, who were searching for clues about a growing problem in the rain forest.
Madidi, a bit smaller than New Jersey, is a stunning natural trove, with more than 11 percent of the world’s bird species and 200 species of mammals. Even in the rainy season, when waist-deep mud can hobble you and insects seem hell-bent on eating you alive, it’s magical. Scarlet macaws swoop overhead, swarms of green-blue Urania moths blanket mud puddles, and the giant trees that loom over all are so lush they block out the sky.
The park is also home to the jaguar, the mysterious spotted cat of the jungle that once roamed from the southwestern U.S. through Argentina. Jaguars have lost swaths of forest habitat to ranchland, farmland, and illegal logging, and they’re often shot by people who fear them (even though jaguars very rarely attack humans) or who worry that the cats will kill their cattle (which they sometimes do). And now jaguars are facing a new threat: poaching for the illegal trade in wildlife.