Male Orangutans Plan Their Trips The Night Before, Loudly Announce Their Itinerary To Females
Sumatran male orangutans plan their travels a day in advance and announce them the night before they set off through the forest, according to a study by researchers from the Anthropological Institute and Musuem in Zurich, Switzerland. The loud vocalizations are known as "long calls," as they can last up to four minutes. The long calls can be heard over a half a mile away, and are emitted by male orangutans wishing to alert female orangutans that they'll be rolling into their neighborhood soon.
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"Basically, they're telling their female audience where they're going," said anthropologist and lead study author Carel va Shaik. The call also serves to warn competitive males to go away.
In the study, researchers followed 15 Sumatran male orangutans in the wild. The researchers tracked the orangutans between 10 and 12.5 hours each day. The night before heading off for a certain area, an orangutan would emit a loud call in that direction, the researchers found. The orangutan would go to sleep, setting off for the planned location 12 hours later. Over the course of 320 days, the researchers saw the orangutans do this repeatedly.
"Instead of shaking his head or turning his body around in all directions, which is what you would expect or what other species do, he looks in one direction very rigidly," said van Shaik. "Instead of broadcasting, it's narrowcasting."
The idea of animals "planning" has been observed in some cases. In California, Western scrub jays were found to store snacks when they detected that food would be scarce later on. Chimpanzees in zoos have been known to stockpile rocks to throw at visitors. Even plants have, in some sense, being observed "planning": in a recent study, researchers found that plants were able to "do math" to adjust their starch consumption levels after dark, ensuring the starch would last through dawn.
Allison Howard, a researcher who studies primate route planning at the University of Georgia, said that other primates have not been observed detailing their travel plans. But Howard (who was not involved in the study) said it's possible that other animals do plan, but we just can't see it.
"We might be missing it in other animals because they don't have calls that indicate direction of travel," Howard said. "Or if they do indicate direction of travel, we don't know what the signal is."
The study, "Wild Orangutan Males Plan and Communicate Their Travel Direction One Day in Advance," was published in PLoS ONE.
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