From the CSNW Blog:

Last night there was a commotion on the hill. We didn't see what happened, but there was a lot of screaming and Negra ran to the greenhouse to seek reassurance from the other chimpanzees. Was it a fight? Did Negra get stung by an insect? Did she touch the electric fence? This morning, as I was getting ready to let the chimps out onto the hill, I wondered if Negra would choose to stay indoors where she felt safe. But before I could unlock the door, Negra was there, waiting. She was the first out the door, and she stayed out long after the other chimps had gone back inside. She looked so at ease, eating grass and soaking up the sun. When it came time for her to get up and head back to the building, something happened - she panicked. I imagine that she didn't realize how far it was back to the greenhouse, sort of like what happens when you climb a tall ladder and don't experience fear until you look down and realize how high up you are. This is probably what happened to her last nig...