Census and distribution of chimpanzees in Côte D’Ivoire

Abstract

ABSTRACT. Most methods of estimating chimpanzee population densities rely on nest counts. We tested the most frequently used techniques on a known chimpanzee community living in the rainforest of the Ta'i National Park, C6te d'Ivoire. The best density estimates are given by counts that 9 assume groups of nests to be distributed randomly and that use the mean group size for homogenous habitat but the median for heterogenous habitats. Correction for real forest cover within the region should be made because chimpanzees make nests only in forested regions. This method gave the exact chimpanzee density for the Ta'i population, i.e. 1.7 nest builders/km 2. For the nationwide survey, we first estimated the chimpanzee density for different types of habitat (e.g. intact primary forest: 1.64 chimpanzees/km2; degraded forests: 0.4 chimpanzees/km2; human encroached forests and mosaic habitats: 0.09 chimpanzees/kmZ). Second, we estimated the total forest cover of the country with satellite pictures. This gave an estimated chimpanzee population in C6te d'Ivoire of about 11,676_+1,168 individuals, which equals the number of spectators at a soccer game in an average European town. Sadly, only three National Parks may have chimpanzee populations large enough to be viable, whereas the rest are scattered and isolated small populations that are already threatened in their survival.

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

“…While chimpanzees in other ecotone regions were found to occasionally nest in woodland savanna (Baldwin et al, 1982;Hicks et al, 2014;McCarthy et al, 2015;Moore and Vigilant, 2013;Ogawa et al, 2007;Pruetz et al, 2008), all 406 chimpanzee nests found in this study were located in CCF, as was also reported for the ecotone of Republic of Côte d'Ivoire (Marchesi et al, 1995). In the CNR, chimpanzees further favor extensive CCF habitat also around their nest sites.…”

“…For the nest production rate we used i) r = 1.14 as reported for three habituated wild chimpanzee communities in Tai National Park, Republic of Côte d'Ivoire (Kouakou et al, 2009) and ii) and r = 1.09, a value often cited in the literature and reported from both the Budongo forest (Plumptre and Reynolds, 1997a) and the lowland tropical forest in northern Congo (Morgan et al, 2006). For the mean nest lifetime t we evaluated 22 studies from 16 different locations across the whole species range of chimpanzees (Blom et al, 2001;Carvalho et al, 2013;Devos et al, 2008;Fleury-Brugiere et al, 2010;Ghiglieri, 1979;Hall et al, 1998;Hicks et al, 2014;Ihobe, 2005;Kouakou et al, 2009;Marchesi et al, 1995;Matthews and Matthews, 2004;Moyer et al, 2006;Ogawa et al, 2006;Reynolds, 1997a, 1996;Pruetz et al, 2002;Serckx et al, 2014;Stewart et al, 2011;Tutin and Fernandez, 1984;Van Krunkelsven, 2001). We then considered the median estimate per location to obtain four different estimates used in this study: the median estimate of all ecotone locations matching our habitat (Lopé NP Gabon, Niokolo Koba NP Senegal, forest-savanna mosaic of western DRC, Ugalla Forest in Tanzania, Haut Niger NP in Guinea and Lagoas de Cufada Natural Park in Gambia, 140 days), the median estimate of all 16 locations (120 days), as well as 1.5 × more and less than this global median (180 and 80 days, respectively).…”

“…Our survey effort was 86.2 km of transect walked in CCF, which constitutes the only habitat used by chimpanzees for nest building according to our observations (see below) and other reports from ecotone habitats (Marchesi et al, 1995). We counted a total of 384 nests and used DISTANCE 6.2 to estimate chimpanzee nest density in our study region from these data based on the half-normal key detection model with lowest Akaike information criterion (Buckland et al, , 2001.…”

<Note> First Assessment of Chimpanzee (Pan troglodytes troglodytes) density and bedding behaviour in the Pongara National Park, Gabon

“…We also reduced the density calculated by 20% to take into account the day bedding activity of the chimpanzee 10,11 .…”

<Notes> Sampling Rapidly Dwindling Chimpanzee Populations

“…al. (7) conducted a survey of chimpanzee populations of COte d'Ivoire in 1991. Based on their findings, we visited a subset of the census sites in 1993-94 and again in 1995 (13 different sites).…”