We trekked beneath the canopy of Kibale National Park, Uganda, led by a ranger and his assistant. The chimpanzee group we found melted into the brush as the emphatic-sounding calls of other chimp groups echoed through the forest. We did our best to keep up with their fluid movements through the undergrowth, scrambling. This led us to a clearing where we encountered the alpha chimpanzee male (left) grooming a younger male, perhaps reinforcing an existing coalition to maintain his dominance. A second young male was assisting in the process.