Status and distribution of Comoe Chimpanzees: combined use of transects and camera traps to quantify a low-density population in savanna-forest mosaic

The West African chimpanzee is critically endangered (CR). From 1990 to 2007, Ivory Coast lost 90% of its population to habitat destruction and poaching. In order to effectively implement conservation measures, we need to determine the status of any remaining populations in the country. The chimpanzee population of Comoe National Park (CNP) was assumed to have been severely depleted following the politico-military crisis of 2002-2011. Surveys in 2007, 2010, 2012, and 2014 failed to find significant evidence of chimpanzees in the park, leading managers to believe that no sustainable population was left. To evaluate status and distribution of chimpanzees in CNP, in 2015 we conducted a stratified survey in our study area in the southwest of the park. Over the next 3 years, we conducted recce walks in the north, east, and center of the park, and in 2017 we collected additional data on distribution of chimpanzees during the full park survey for elephants. Additionally, for the first time in northern Ivory Coast, we carried out a local nest decay study. In our main study area, we estimated a density of 0.14 weaned chimpanzees/km(2), with an abundance of 127 (92-176) weaned chimpanzees, representing a sustainable population in CNP. We identified 123 individual chimpanzees via parallel camera-trap survey. We discovered a resident chimpanzee population to the east of the Comoe River, an area previously assumed devoid of chimpanzees. This study confirms the viability of a population key for the conservation of Western chimpanzee. We stress the importance of concentrating stratified surveys in potential wildlife habitat to determine the distribution of this and other cryptic threatened species.