Chimps are actually pretty hard to photograph in the wild. They usually hang out high in the tree tops and are very active, ducking in and out of thick vegetation. I was lucky to encounter a troop at the end of the day in Queen Elizabeth National Park in Uganda, fairly low to the ground. I was able to get very close to this young lady and had just enough light before the sun disappeared.
Nikon D700 with Nikkor 200-400mm lens (at 350mm) ISO 800, f/4 at 1/200th of a second