Scientists at The University of Manchester in Britain spent a year at a research facility in Indonesia observing and filming orangutans, one of man's closes relatives, building large, oval nests daily in tree canopies where they sleep overnight.
The choice of a tree-top nest is possibly for protection from predators and parasites or for warmth during sleep, they said.
The orangutans used particular branches for different parts of the nest and also broke the branches in different ways depending on how they would be used, researchers observed.
"We found that the orangutans chose strong, rigid tree branches for the structural parts of the nests that supported their weight, and weaker, more flexible branches for the nest's linings, suggesting that the apes' choice of branch for different parts of the nests was dictated by the branches' diameter and rigidity," researcher Roland Ennos reported in a Manchester release Tuesday.
"Further, branches chosen for the nests' structural framework were fractured differently from those chosen for the lining: whereas structural branches were broken halfway across, leaving them attached, branches used for lining were completely severed, suggesting that orangutans might use knowledge of the different ways in which branches break to build strong and comfortable nests," Ennos said.
"Our research has implications for the evolution of intelligence and cognition as well as the evolution of tool use in early humans. It provides evidence that the development of all these traits started in apes because of their need to understand their mechanical environment, not just their social environment."