After several years tracking orangutans in the Sumatran swamplands, researchers made some surprising discoveries, they report in the journal PLoS One: males make travel plans up to 24 hours in advance and share them with nearby orangutans by emitting long, loud calls that can be heard more than a half-mile away.

Their cheek pads act as a funnel, amplifying their calls like a megaphone.

“Males emitted long calls mostly facing the direction they traveled a few hours later, or even after a night’s rest,” said one of the researchers, Karin Isler of the Anthropological Institute and Museum in Zurich. Hearing a call, interested females might come closer to stay in contact, while nondominant males might flee to avoid a confrontation. The orangutans usually traveled about a half-mile a day, often looking for fruit from trees.