First quantitative survey delineates the distribution of chimpanzees in the Eastern Central African Republic

Abstract

A B S T R A C TVast, pristine ecosystems and their biodiversity are vanishing globally at frightening speed, but many large tracts of wilderness have not yet been systematically inventoried and important natural populations of threatened species remain poorly characterized. The forest-savanna ecotone of the Eastern Central African Republic (CAR) is one such poorly studied area. Using camera traps, transect walks and collected fecal samples, we provide the first quantitative survey of chimpanzees (Pan troglodytes) in this region previously classified as a highly important chimpanzee conservation unit. In contrast to species distribution models and expert predictions, we did not find any evidence of chimpanzees in the large and remote forest blocks west of the Chinko River despite considerable search effort. Our study thus highlights the limitations of relying solely on remote sensing data to predict the presence or absence of endangered species and illustrates the necessity of extensive field surveys to accurately assess occurrence and density in remote areas. However, we did discover a sizeable and reproducing population of chimpanzees east of the Chinko River. Based on a density of 0.81 chimpanzees/km 2 in closed canopy forest that we inferred from nest count data, we estimate 910 weaned chimpanzees to inhabit the Chinko Nature Reserve (CNR) and further predict additional 2700 individuals in adjacent, unmanaged hunting zones and reserves. According to microsatellite data, these chimpanzees genetically cluster with P. t. schweinfurthii populations in East Africa. Conservation action and appropriate management plans are urgently needed to protect this important population and to prevent heavily-armed nomadic pastoralists from the Sahel, illegal miners, as well as elephant and meat poachers, from irretrievably destroying the natural vegetation and local biodiversity of the area.

Apex predators decline after an influx of pastoralists in former Central African Republic hunting zones

“…Annual precipitation, mostly accumulating during the rainy season from May to October, varies from 1 340 to 1 740 mm on a northeast to southwest gradient (Fick et al, 2017). So far, our ongoing surveys have identified flagship species like the Eastern giant eland (Tragelaphus derbianus gigas) (Brandlová et al, 2018), both African elephants (Loxodonta cyclotis and L. africana), giant forest hog (Hylochoerus meinertzhageni), common hippopotamus (Hippopotamus amphibius), Eastern chimpanzee (Pan troglodytes schweinfuthii) (Aebischer et al, 2017) and 26 different carnivore species.…”

A sparse observation model to quantify species interactions in time and space

“…We applied Tomcat to camera trapping data obtained during the dry seasons from 2012 to 2018 from a region in the eastern Central African Republic (CAR), a wilderness exceeding 100,000 km 2 without permanent settlements, agriculture or commercial logging (Aebischer et al, 2017). The available data was from 1,059 camera traps set at 532 distinct locations that cover the Aire de Conservation de Chinko (ACC), a protected area of about 20,000 km 2 .…”

“…For more information about camera deployment and sampling design, see Aebischer et al (2017). Here, we focus on duikers Cephalophinae, which are a diverse mammalian group common in the data set and for which near-perfect manual annotation was available.…”

“…To infer habitat preferences for these species, we benefited from an existing land cover classification at a 30m resolution that represents the five major habitat types of the Chinko region: moist closed canopy forest (CCF), open savanna woodland (OSW), dry lakéré grassland (DLG), wet marshy grassland (WMG) and surface water (SWA) (Aebischer et al, 2017). Around every camera trap location and at 10,200 regular grid points spaced 2.5 km apart and spanning the entire ACC, we calculated the percentage of each of these habitats in 11 buffers of sizes 30; 65; 125; 180; 400; 565; 1260; 1785; 3,990; 5,640 and 17,840 meters.…”

“…We used Tomcat to study the spatio-temporal distribution and overlap of duikers Cephalophinae in the eastern Central African Republic (CAR). We benefited from existing camera trapping data (Aebischer et al, 2017), collected between 2012 and 2018 at 532 distinct locations in the Aire de Conservation de Chinko (ACC), a protected area of about 20,000 km 2 that was established in 2014 by the government of the CAR in former hunting zones.…”