Why do chimpanzees die in the forest? The challenges of understanding and controlling for wild ape health.

Tourists from all over the world travel to different African countries to see the great apes in their natural environment. This is a booming component of the ecotourism market. But what is the risk of disease transmission when humans are in close proximity to the apes [Butynski & Kalina, 1998; Wallis & Lee, 1999]? Our recent publication provided the first clear evidence of transmission of respiratory disease from humans to chimpanzees [Köndgen et al., 2008]. At the same time many remain skeptical of the magnitude of such a risk or may think we cannot ask tourists to wear surgical masks. First, I want to provide an account of how we were forced to become convinced that disease is a central issue to ape survival. Second, I want to address some of the important challenges that we have to resolve in order to understand the natural causes of mortality in wild chimpanzees and how we can protect them from disease risks.