Absence of evidence is not evidence of absence: Discovery of a large, continuous population of Pan troglodytes schweinfurthii in the Central Uele region of northern DRC

• Published in: Biological conservation 2014-03, Vol.171, p.107-113
• Main Authors: Hicks, Thurston C., Tranquilli, Sandra, Kuehl, Hjalmar, Campbell, Geneviève, Swinkels, Jeroen, Darby, Laura, Boesch, Christophe, Hart, John, Menken, Steph B.J.
• Format: Article
• Language: English
• Subjects: Abundance; Animal, plant and microbial ecology; Applied ecology; Bili-Uéré Protected Area Complex (BUPAC); Biological; Biological and medical sciences; Bushmeat; Chimpanzees; Conservation; Conservation, protection and management of environment and wildlife; Eastern chimpanzee (Pan troglodytes schweinfurthii); Encounters; Forests; Fundamental and applied biological sciences. Psychology; General aspects; Landscapes; Line transect surveys; Monitors; Pan troglodytes; Pan troglodytes schweinfurthii; Parks, reserves, wildlife conservation. Endangered species: population survey and restocking; Pictures; The Democratic Republic of the Congo (DRC)
• ISSN: 0006-3207; 1873-2917
• DOI: 10.1016/j.biocon.2014.01.002

•We present the results of our 2004–2009 chimpanzee survey of the northern DRC, as well as a re-survey in 2012.•The Central Uele and neighboring regions are home to one of the largest remaining continuous population of Eastern chimpanzees.•In the core area of the Gangu Forest, chimpanzee nest encounter rates remained constant between 2005 and 2012.•The chimpanzees are falling under increasing threat from the bushmeat trade. With great ape populations in decline across much of their range, it is crucial to obtain a global picture of their distribution and abundance, in order to guide conservation activities and to provide baseline data against which to monitor their trends. Although great apes are popular, charismatic species, we still do not possess a complete understanding of their distribution and abundance, which hinders their long-term protection. We highlight this problem by providing information on the distribution and abundance of the Eastern chimpanzee (Pan troglodytes schweinfurthii) in the northern Democratic Republic of the Congo (DRC), a region which has until now received little attention. We conducted a standing crop nest survey in the Bili area in 2005 and exploratory reconnaissance walks (recces) across the Bas-Uele region between 2004 and 2009. At Bili, the nest encounter rate in the remote forest was 4.84nests per km (CI=2.78–8.55) and in the area closer to the road it was 1.92nests per km (CI=1.08–3.43). In 2012, we repeated a part of the original transect survey and found that the nest encounter rate had remained stable over that period. On our recce walks across the region, we encountered chimpanzee nests in all forests surveyed, and within 13km of the largest population centers. Our results suggest that the Central Uele landscape and neighboring regions are home to one of the largest remaining continuous populations of Eastern chimpanzees, that extends across at least 50,000km2, likely representing thousands of individuals, but which is falling under increasing pressure from habitat destruction, mining and the bushmeat trade. This population has until now remained hidden from researchers and is not protected. Our results reflect gaps in our current understanding of ape distribution and abundance, and highlight the importance of obtaining more sound and complete data before assessing species status and making recommendations to guide conservation efforts.