But the rangers had already made a difference. They had established a government presence in a region where previously anything went. Thanks to their performance in San Martín, they were invited in November to participate in the annual parade in honor of the cuadrillas. Mr. Zorro thought the invitation was a turning point for the park, a moment of acceptance. And during their motorcycle patrols through Manacacías, the rangers had recorded a number of significant wildlife sightings.

Gustavo Castro, one of the rangers staying at the ranch that week, had been standing at a lookout a few months earlier when he saw something brown and hairy scurrying around in the tall grass. “I got closer to him, maybe five or six meters, and he continued normally,” Mr. Castro said. “I was able to get some good videos and photos.” The animal was a bush dog, a wild dog that was thought to be extinct in the area.

For Dr. Walschburger, the verified sighting of a forest dog was exciting. Bush dogs were more common in the Amazon region, indicating that the wilderness corridor between Manacacías and the Amazon basin was active. The forest dog's documented use of the area could potentially result in stronger protection of that corridor, which on a satellite map looked like a curved green finger extending to the southeast. The more data comes out of the park, said Dr. Walschburger, the greater the opportunities for nature conservation in and around the park.

The llanos can be disorienting – the German explorer Alexander von Humboldt, who explored the Orinoco region in 1800, complained of their “infinite monotony” – but after months of patrols, the new rangers navigated the terrain with ease. Their phones were now full of oncillas, tapirs, great horned owls and the gleaming crowns of Mauritius palms at sunset.

Oscar Rey joined his colleagues as they stopped at a bend of the Manacacías River. The rangers regularly checked in on this sandy coastline, while people routinely placed fishing nets over it. Mr. Rey has known it since he was a boy, when his grandfather taught him to shuffle while walking barefoot in the water to avoid being stung by stingrays.

All around him were tracks of tapirs, peccaries, capybaras and lizards. It was almost that time of year when freshwater turtles were digging nests in the riverbanks, he said. Mr. Rey's grandparents ate their eggs, of course, but future generations did not.