young's hill

When free-living chimpanzees prepare to bed down for the night, most build nests high up in the trees. The reason they do this, as far as we know, is to protect themselves from ground-dwelling predators (though one adventurous researcher discovered some other advantages). Captive chimpanzees, while not at risk of predation, also build nests. The methods for building a nest are culturally learned, but the urge itself is instinctual.

Sometimes I try to imagine what that urge feels like to them. They seem to thoroughly enjoy the process and the ritual of nest-building. Jody, in particular, seems like she is in a state of meditation when she is folding and weaving her blankets. Missy spins 360 degrees as she makes her nest to ensure that each section is symmetrical. Jamie weaves some of her blankets through the caging, as if she is anchoring her nest to the building. The details are different in each case, but each portrays a sense of calmness and comfort throughout the process.

When we sleep we are vulnerable, and nests help chimps feel safe and secure. It’s interesting to note that captive chimpanzees build nests with high sides just like their wild counterparts do to keep from falling out of the tree in the middle of the night. But captive chimps are usually sleeping on the floor or on platforms where there is no risk of falling. And often their nests consist only of sides – there is no bottom. Sometimes the nests look like a doughnut with bare floor in the middle. It’s obvious that the nest is not serving the function of a mattress, to cushion them from the hard ground. Instead, I think it’s fulfilling an instinct that probably goes back millions of years – the urge to be safe and secure, the urge that keeps a sleeping chimpanzee up in the tree where they belong.

This also explains why chimpanzees usually make nests in areas where they feel at ease. You want to close your eyes knowing that nothing strange will happen while you are asleep. At CSNW, the chimps almost always make their night nests on the second story of the playroom or on the benches high up in the front rooms. In the first year that the chimps had access to Young’s Hill, not once did we see someone make a nest outside. But this morning, Jody decided to be the first, and dragged her blankets outside.

This was a big step for Jody, and I think it demonstrates a level of comfort on the hill that we haven’t seen yet. You’ll notice that she made her nest next to the vehicle access gate – the only section of caging on the two-acre enclosure. We often talk about the chimps making gradual transitions, and I think this is a good example. She wants to make a nest outside, but she insists on the security and familiarity of caging as her backdrop.

She didn’t stay in her nest very long, but we are thrilled that she has taken this first step.