[not included: morotopith hanging orthogrady, raptorial mimicry, human dome hut derivation]
Nest-building orangutans demonstrate engineering know-how to produce safe,
Adam van Casteren cs 2012 PNAS
Orangutans must daily build safe & comfortable nest structures in the
they do this quickly & effectively, using the branches that surround them.
We measured the whole nest compliance & the thickness of the branches
used, and recorded the ways in which the branches were fractured.
Branch samples were also collected from the nests, and subjected to
3-point bending tests to determine their mechanical properties.
- The center of the nest is more compliant than the edges. This may add
extra comfort & safety to the structure.
- During construction, orangs use the fact that branches only break
half-way across in "green-stick" fracture to weave the main nest
structure. They choose thicker branches with greater rigidity & strength
to build the main structure in this way.
- They then detach thinner branches by following greenstick fracture with
a twisting action to make the lining.
These results suggest that orangutans exhibit a degree of technical
knowledge & choice in the construction of nests.