Orangutans not only plan their travel routes in advance, but they also inform others about their trip a day ahead of time.
This very human-like behavior implies other things about orangutans.
"Our study makes it clear that wild orangutans do not simply live in the here and now, but can imagine a future and even announce their plans," primatologist Carel van Schaeik of the University of Zurich, who conducted the study, was quoted as saying in a press release.
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"In this sense, then, they have become a bit more like us," he added.
The findings are published in the latest PLoS ONE.
The study must have been arduous. For years, Van Schaeik and his team followed wild orangutans throughout the dense tropical swamplands of Sumatra. As they did so, they noted the orangutans' vocalizations, body language, travel and more.
Adult males are the ones who travel the most among orangutan groups. They usually head out into the forest alone, but they also maintain social relationships with potential female mates and other males. The males fall into a hierarchy, with dominant and more submissive orangutans in the mix.