In an article published September 11 in the open access journal PLOS ONE (“Wild Orangutan Males Plan and Communicate Their Travel Direction One Day in Advance”), researcher Carel van Schaik and colleagues from the Anthropological Institute and Museum in Zurich, Switzerland present their findings after studying male and female orangutans in the Sumatran tropical forests.
The researchers set to discover whether or not great apes can plan for future needs in the wild. Previous studies have shown that great apes can plan for future needs, but that conclusion was reached based on the study of great apes in captivity.
In this study, authors surveyed the songs of orangutans that live in dense tropical forests, often beyond visual range of others in their population. Adult males produce loud, long vocalizations capable of being heard nearly a mile away – ostensibly to establish their status amongst other males or call out to females.
The researchers tracked over 200 calls made by 15 adult males in the wild, and found that males faced the direction they planned to travel and produced “long calls” in that direction the night in advance of a journey. If the itinerary changed the following morning, males were more likely to follow up with a call in the new direction planned.
“We found that males emitted long calls mostly facing the direction they travelled a few hours later, or even after a night’s rest,” said study coauthor Karin Isler.
Females within hearing range recurrently followed the path taken by the male and changed direction when the male did. Lesser males who heard these calls were subsequently inclined to avoid following a comparable path.
Scientists are still unclear as to when orangutans choose to plan their trips; however, some of the whys and wherefores proposed include avoidance of a known rival, and searching for mates or food. The researchers also explained that such preparation capacities may not be limited to orangutans – they may exist in other apes or large-brained animals as well.