Ebola and the decline of gorilla Gorilla gorilla and chimpanzee Pan troglodytes populations in Minkebe Forest, north-eastern Gabon

During 1998-2000 extremely low densities of gorillas Gorilla gorilla gorilla and chimpanzees Pan troglodytes troglodytes were found in the Minkebe Forest block in north-eastern Gabon. When compared with data collected before 1994, these data suggest a catastrophic decline in ape populations in the area. We believe that this decline was caused by a disease epidemic. The period of decline corresponds with the Ebola outbreaks of 1994 and 1996 that occurred in the human population in the same area. Deaths of gorillas and chimpanzees were associated with both Ebola outbreaks. Data from nearby sites indicate that the epidemic was limited to the Minkebe Forest. Occurrence of such epidemic die-offs should be taken into account in conservation strategies for the long-term survival of ape populations. At the time of writing, an Ebola epidemic among humans in the Zadie Department east of Minkebe Forest has resulted in 53 deaths. In the neighbouring Republic of Congo, authorities have reported 43 deaths and at least 12 other cases of Ebola. These epidemics are believed to be linked to the handling and eating of dead apes.