Orangutans Plan Their Trips

A male Sumatran  orangutan. Photo by Mikaku / Flickr Creative Commons

When you take a trip back to your hometown, do you call your friends to let them know you’re coming? Well, you are not the only one because it turns out that wild male Sumatran orangutans likely do something similar. A recent study, published in PLoS One, suggests that the apes communicate their travel plans with their peers up to a day ahead of time. They have a special facial feature in the form of big puffy cheek pads that allow them to send the message over long distances. Sometimes, the sound can carry almost a mile. The pads perform like a megaphone, amplifying the male’s thunderous cries, which primatologists refer to as “long calls.”

A dominant male orangutan will make these long calls so that the others act according to his travel plans. “They are calling to let their female friends know where they will be so the [females] can remain within earshot,” explained van Schaik. Females will approach the sound of the call, either for the chance to mate or to receive protection from bothersome non-dominant males. These non-dominant males, on the other hand, will hear the roar and flee in the opposite direction.

It has been long assumed that only human beings can plan for the future because they alone have the ability to anticipate what lies ahead. Animals were believed to be creatures of the moment, responding to immediate needs, such as hunger, thirst, fear or fatigue. Lately, new studies have suggested that animals, most notably great apes, are capable of advanced planning, self-control and episodic memory. For example, a Science study published in 2006 found that zoo orangutans and bonoboos chimpanzees could choose, hide, and store tools, then remember where to find them up to fourteen hours later when they needed them. Lead study author Dr. Carel van Schaik said he was attracted to studying Sumatran orangutans because they are famous for their tool use, and he was interested in learning more about their social organization and their culture.  

Van Schaik and his colleagues conducted this newly published research in Suaq Balimbing, a peat swamp forest in the Indonesian Gunung Leuser National Park by recording 1,169 long calls made my these male pot-bellied creatures. They observed that the dominant males would emit these calls in the direction of their planned travel route.  Not only that, but they would broadcast each time change in their direction.  They found that the red-haired apes would also send a directional call the night before going to sleep, and then keep to that direction the next morning, for up to 22 hours after they announced their plan. The researchers concluded that the directional commitment to the previous night’s call proved that the orangutans were not just responding to their immediate needs, but that they were traveling through the forests based on the long-term plans they had devised.  The scientists also found that other orangutans would continue to react correctly to the long call of the previous evening, even if they didn’t hear anything the next morning. 

“We show that it does not take language to do some planning for the future,” said van Shaik. He was quick to point out, however, that the results of this study do not necessarily suggest that orangutans are like humans in that they can set distant goals, or that they can ponder the future. 

For van Shaik, the next step is examining whether this pattern will hold true with the darker red haired Bornean orangutans. “We now want to compare these Sumatrans with the Bornean, which have a different social structure,” he said.  “[They] probably announce their plans in another way.”

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