"This guy basically thinks ahead," van Schaik said. "They're continuously updating their Google Maps so to speak. Based on that, they're planning what to do next."
The apes didn't just call once, but they keep at it, calling more than 1,100 times over the 320 days.
"This shows they are very much like us in this respect," van Schaik said. "Our earliest hominid ancestor must have done the same thing."
Scientists had seen such planning in zoos and controlled experiments, but this study provides solid evidence of travel planning in the wild, said Frans de Waal of Atlanta's Emory University, who was not part of the study.
Van Schaik said he and colleagues happened upon the trip calls by accident nearly 20 years ago, first with the dominant male Arno, who they followed more than the other 14 males. They waited to publish the results because he thought few people would believe orangutans could do such planning. But in recent years, the lab and captivity studies have all shown such planning.
Based on previous studies and monitoring, van Schaik figured the male lets the world know his plans so females can come to him or stay close. Some females may want to stay within earshot in case they are harassed by other males and need protection. Others can come to mate.
- AP