title: Density estimates and nesting-site selection in chimpanzees of the Nimba Mountains, Côte d'Ivoire, and Guinea.
abstract: We investigated nesting behavior of non habituated chimpanzees populating the Nimba Mountains to document their abundance and their criterions of nesting-site selection. During a 19-month study we walked 80 km of transects and recces each month, and recorded 764 nests (mean group size = 2.23 nests) along with characteristics of vegetation structure and composition, topography, and seasonality. Population density estimated with two nest count methods ranged between 0.14 and 0.65 chimpanzee/km(2) . These values are lower than previous estimates, emphasizing the necessity of protecting remaining wild ape populations. Chimpanzees built nests in 108 tree species out of 437 identified, but 2.3% of total species comprised 52% of nests. Despite they preferred nesting in trees of 25-29 cm DBH and at a mean height of 8.02 m, we recorded an important proportion of terrestrial nests (8.2%) that may reflect a cultural trait of Nimba chimpanzees. A logistic model of nest presence formulated as a function of 12 habitat variables revealed preference for gallery and mountain forests rather than lowland forest, and old-growth forest rather than secondary forests. They nested more frequently in the study area during the dry season (December-April). The highest probability of observing nests was at 770 m altitude, particularly in steep locations (mean ground declivity = 15.54%). Several of the reported nest characteristics combined with the existence of two geographically separated clusters of nest, suggest that the study area constitutes the non-overlapping peripheral areas of two distinct communities. This nest-based study led us to findings on the behavioral ecology of Nimba chimpanzees, which constitute crucial knowledge to implement efficient and purpose-built conservation.
authors.affiliation: Biology Ecology and Evolution, University of Liège, Liege, Belgium.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Granier
authors.forename: Alain
authors.initials: A
authors.lastname: Hambuckers
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Matsuzawa
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Huynen
mesh_terms: D000818:Animals; D003247:Conservation of Natural Resources; D007560:Cote d'Ivoire; D017753:Ecosystem; D065928:Forests; D016701:Guinea; D009425:Nesting Behavior; D002679:Pan troglodytes / Q000523:psychology*; D011156:Population Density; D012621:Seasons; D014197:Trees
keywords: behavioral ecology; chimpanzee; conservation; nest count; nesting-site selection