The Critically Endangered western chimpanzee declines by 80%

Abstract

African large mammals are under extreme pressure from unsustainable hunting and habitat loss. Certain traits make large mammals particularly vulnerable. These include late age at first reproduction, long inter-birth intervals, and low population density. Great apes are a prime example of such vulnerability, exhibiting all of these traits. Here we assess the rate of population change for the western chimpanzee, Pan troglodytes verus, over a 24-year period. As a proxy for change in abundance, we used transect nest count data from 20 different sites archived in the IUCN SSC A.P.E.S. database, representing 25,000 of the estimated remaining 35,000 western chimpanzees. For each of the 20 sites, datasets for 2 different years were available. We estimated site-specific and global population change using Generalized Linear Models. At 12 of these sites, we detected a significant negative trend. The estimated change in the subspecies abundance, as approximated by nest encounter rate, yielded a 6% annual decline and a total decline of 80.2% over the study period from 1990 to 2014. This also resulted in a reduced geographic range of 20% (657,600 vs. 524,100 km ). Poverty, civil conflict, disease pandemics, agriculture, extractive industries, infrastructure development, and lack of law enforcement, are some of the many reasons for the magnitude of threat. Our status update triggered the uplisting of the western chimpanzee to "Critically Endangered" on the IUCN Red List. In 2017, IUCN will start updating the 2003 Action Plan for western chimpanzees and will provide a consensus blueprint for what is needed to save this subspecies. We make a plea for greater commitment to conservation in West Africa across sectors. Needed especially is more robust engagement by national governments, integration of conservation priorities into the private sector and development planning across the region and sustained financial support from donors.

Advancing conservation planning for western chimpanzees using IUCN SSC A.P.E.S.—the case of a taxon-specific database

“…Overall, our abundance estimates are in line with previous studies that estimated around 7000 chimpanzees in Liberia (Tweh et al 2015), 5600 in Sierra Leone (Brncic et al 2015), and 17 700 in the Guinean part of the Fouta Djallon (WCF 2012). Kühl et al (2017) compiled abundance data for 35 sites across West Africa, covering 40% of the western chimpanzee range, and estimated a Figure 5. Cumulative proportion of western chimpanzees living within increasing distance to (a) 'development corridors', (b) roads, and (c) settlements.…”

Stable isotope variation in savanna chimpanzees (Pan troglodytesverus) indicate avoidance of energetic challenges through dietary compensation at the limits of the range

“…Because tissues used for stable isotope analyses (e.g., hair, teeth, and bone) reliably record the nature of isotopic intake, isotope ecology has recently gained popularity in primatological research (Crowley, Rasoazanabary, & Godfrey, ; Oelze et al, ; Sandberg, Loudon, & Sponheimer, ; Schoeninger, ; Schoeninger, Iwaniec, & Nash, ). Furthermore, a particular advantage of using δ 13 C and δ 15 N as dietary indicators is the possibility to incorporate otherwise unobtainable data on groups unhabituated to researcher presence in the face of rapid species decline (e.g., Kühl et al, ).…”

Nest-Building Behaviour by Chimpanzees (Pan troglodytes verus) in the Non-Protected Area of Diaguiri (Kedougou, Senegal): Implications for Conservation

“…The West African chimpanzee (P. t. verus) is one of the most threatened subspecies [Kormos and Boesch, 2003]; it was relisted as Critically Endangered in 2016 due to significant regional-wide population declines [Humle et al, 2016;Kühl et al, 2017]. Conserving these great apes requires a detailed understanding of their population size, spatial distribution and demographic trends.…”