I am napping in a chimpanzee nest, 12 metres above the ground in Uganda’s Toro-Semliki Wildlife Reserve. Sleep comes easier than you might expect. The nest is surprisingly well-engineered: springy, cupped and stable in a way that feels less like a pile of branches than a purpose-built piece of furniture. Then I wake up. I am suddenly, acutely aware that I am not in bed, but balanced high in the ca...