At the end of each day, free-living chimpanzees build elaborate nests and go to sleep for the night. These night nests, typically built high up in the crown of a tree, are thought to serve a number of functions including thermoregulation, protection from predators and parasites, and shelter from the elements. According to one researcher who spent time sleeping both on the ground and in chimpanzee nests, they may also simply provide a more comfortable night’s rest. Chimpanzees spend considerable time selecting the proper trees and branches on which to build their nests and then weaving smaller branches and leaves together to form a mattress or basket. This investment of time and energy makes sense; after all, once they are asleep, it is only the quality of their nest keeping them from falling to the ground below.
Day nests, by contrast, are hastily constructed and typically far less structurally complex. They are also more likely to be made on or near the ground. Day nests are simply a place to relax for a moment before the group moves on to another spot.
The chimps at CSNW tend to follow a similar pattern when it comes to the elevation of their nests. Jamie and Foxie in particular regularly make their day nests on the floor of the playroom or front rooms but will make their night nests almost exclusively on elevated benches or catwalks (while Foxie doesn’t build elaborate nests like the others, she does engage in rudimentary nesting behavior). The biggest difference between the nests of the Cle Elum Seven and those of their wild counterparts is that the Seven’s day and night nests are equally complex. Perhaps this can be explained by the fact the the Cle Elum Seven don’t travel very far during the day, and thus they are free to spend as much time in their days nests as they’d like or even return to them throughout the day if they so choose.
In fact, it’s possible that Jamie’s day nests are even more complex than her night nests. This afternoon I watched her make a nest on the playroom floor. With her new favorite boots tucked into her “pelvic pocket,” she twirled fleece blankets in circles around her for several minutes, pushing and pulling each one to form the perfect shape. Then she carefully wove the ends of those blankets through nearby caging, as if to anchor the otherwise unstable nest to something sturdy. She pulled two of her new books close by, one on tractors and another on the chimpanzee children of Gombe, so that she could flip through them as she drifted off to sleep. To top things off, she pulled the last blanket over herself. With each step of this elaborate process she let out a low moan – a sign of contentment.
