In early October, inhabitants of three small indigenous villages along Peru’s remote Alto Purús river returned home from voting in local elections to find that intruders had stolen many of their valuables. Gone were solar panels, shortwave radios, and shotguns. The raiders had also left a cooking fire burning next to a house, setting fire to it. Following the forest trails of the perpetrators, trackers found something disturbing: Remains of the stolen goods littered campsites made by an isolated tribe in the region.

Normally quiet and reclusive, the tribespeople had no use for solar panels or radios. In fact, they did not even seem interested in carrying them back to their home deeper in the forest. Although thefts of clothes, food, or machetes had occurred before, raiding for these kinds of goods—which were costly but useless to the intruders—was a rare act of “hostility,” notes Chris Fagan, executive director of the Upper Amazon Conservancy, a nongovernmental organization headquartered in Jackson, Wyoming, that aims to protect the Amazon headwaters and its indigenous peoples. “We are seeing a dramatic change in behavior of these [isolated] people throughout the Peru-Brazil border.”