			Home About us Contact

Nest Counts (nest + count)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

A survey of the apes in the Dzanga-Ndoki National Park, Central African Republic: a comparison between the census and survey methods of estimating the gorilla (Gorilla gorilla gorilla) and chimpanzee (Pan troglodytes) nest group density

AFRICAN JOURNAL OF ECOLOGY, Issue 1 2001
A. Blom
Abstract A survey of apes was carried out between October 1996 and May 1997 in the Dzanga sector of the Dzanga-Ndoki National Park, Central African Republic (CAR), to estimate gorilla (Gorilla gorilla gorilla) and chimpanzee (Pan troglodytes) densities. The density estimates were based on nest counts. The strip transect census and the line transect survey method (Standing Crop Nest Count) were used to estimate the gorilla nest group density. The strip transect has been most commonly used to date. It assumes that all nest groups within the width of the strip are detected, but as this assumption is easily violated in the dense tropical rain forest, the line transect survey was also used. In this method, only the nest groups on the transect line itself should be detected. This method proved to be an adequate and easy technique for estimating animal densities in dense vegetation. The gorilla density of 1.6 individuals km,2 (line transect survey method) found for the Dzanga sector is one of the highest densities ever reported in the literature for the Western lowland gorilla. The density estimate for chimpanzees was 0.16 individuals km,2 (census method). The results of this study confirm the importance of the Dzanga-Ndoki National Park for primate conservation. Résumé Entre octobre 1996 et mai 1997, on a étudié les grands singes du secteur de Dzanga dans le Parc National de Dzanga-Ndoki, en République Centrafricaine (RCA), pour évaluer les densités de gorilles (Gorilla gorilla gorilla) et de chimpanzés (Pan troglodytes). Les estimations de densité se basaient sur le comptage des nids. On a utilisé le recensement par bande transect et la méthode de contrôle par transect linéaire (comptage réel des nids) pour estimer la densité des groupes de nids de gorilles. C'est la bande transect qui est la plus communément utilisée à ce jour. Cela suppose que l'on détecte tous les groupes de nids inclus dans la largeur de la bande, mais comme cette supposition est facilement mise en défaut dans la forêt tropicale humide dense, on a aussi utilisé la méthode des transects en ligne. Avec cette méthode, seuls les groupes de nids qui sont sur la ligne de transect doivent être détectés. Cette méthode s'est révélée une technique adéquate et facile pour estimer les densités animales dans la végétation dense. La densité des gorilles (1,6 individus / km2) relevée pour le secteur de Dzanga est une des plus élevées jamais reportées dans la littérature pour le Gorille de plaine occidental. On a estimé la densité des chimpanzés à 0,16 individus / km2 (par la méthode de recensement). Les résultats de cette étude confirment l'importance du Parc National de Dzanga-Ndoki pour la conservation des primates. [source]

Estimating chimpanzee population size with nest counts: validating methods in Taï National Park

AMERICAN JOURNAL OF PRIMATOLOGY, Issue 6 2009
Célestin Yao Kouakou
Abstract Successful conservation and management of wild animals require reliable estimates of their population size. Ape surveys almost always rely on counts of sleeping nests, as the animals occur at low densities and visibility is low in tropical forests. The reliability of standing-crop nest counts and marked-nest counts, the most widely used methods, has not been tested on populations of known size. Therefore, the answer to the question of which method is more appropriate for surveying chimpanzee population remains problematic and comparisons among sites are difficult. This study aimed to test the validity of these two methods by comparing their estimates to the known population size of three habituated chimpanzee communities in Taï National Park [Boesch et al., Am J Phys Anthropol 130:103,115, 2006; Boesch et al., Am J Primatol 70:519,532, 2008]. In addition to transect surveys, we made observations on nest production rate and nest lifetime. Taï chimpanzees built 1.143 nests per day. The mean nest lifetime of 141 fresh nests was 91.22 days. Estimate precision for the two methods did not differ considerably (difference of coefficient of variation <5%). The estimate of mean nest decay time was more precise (CV=6.46%) when we used covariates (tree species, rainfall, nest height and age) to model nest decay rate, than when we took a simple mean of nest decay times (CV=9.17%). The two survey methods produced point estimates of chimpanzee abundance that were similar and reliable: i.e. for both methods the true chimpanzee abundance was included within the 95% estimate confidence interval. We recommend further research on covariate modeling of nest decay times as one way to improve the precision and to reduce the costs of conducting nest surveys. Am. J. Primatol. 71:447,457, 2009. © 2009 Wiley-Liss, Inc. [source]