![]() In comparison with “core” habitats, populations in marginal habitats are sometimes representations of range disequilibrium and are typically population sinks characterized by low densities as well as low rates of survival and reproduction, which are largely sustained by immigration ( Pulliam, 2000 Kawecki, 2008 Sexton et al., 2009). In this sense, marginal habitats therefore can be defined as “edge of niche” habitats, in which “environmental conditions in the area represent only a marginal part of the species' fundamental niche” (pg. These habitats typically represent “fuzzy transitional zones” between habitats in which conditions are favorable and those which are inhospitable, and fall beyond the limits of the “n-dimensional niche space” of a species ( Hutchinson, 1961 Holt, 2009). ![]() Marginal habitats, typically peripheral in a spatial perspective of a species' biogeographic range ( Kawecki, 2008 Sexton et al., 2009), are useful in understanding a species' ecological niche and therefore its environmental tolerance. Hence, categorizing savanna habitats as universally more severe and challenging to chimpanzees than more heavily forested habitats does not yet appear to be warranted. However, Taï chimpanzees also faced dehydration as a limitation, which highlights that chimpanzees may experience certain challenges ubiquitously across their range, while other challenges remain habitat-specific. It appears that extreme savanna-mosaic habitats represent a limit to the chimpanzee ecological niche with regard to thermoregulation, in that seasonal environmental conditions, namely the hot and dry conditions of the dry season, strain an individual's ability to maintain homeostasis. Overall, these results supported the assertion that Fongoli as a savanna-mosaic habitat is more extreme in its climate and ecology than a forested site. Although chimpanzees at both sites demonstrated significant seasonal effects of dehydration (creatinine), the more extreme environmental variation at Fongoli promoted higher physiological seasonal costs in the form of elevated cortisol levels. Although living in an extreme and seasonally more variable environment, Fongoli chimpanzees were more stable in their c-peptide values than Taï chimpanzees, but showed more extreme variation in their cortisol values. We found that Fongoli was both more extreme and seasonal in climatic measures like temperature and rainfall, although food availability was more variable at Taï than at Fongoli. We accomplished this using urinary biomarkers of hydration (creatinine), energetic status (c-peptide), and stress (cortisol) collected simultaneously from research stations at each location. ![]() We therefore compared seasonal variation in physiological responses to climatic and ecological factors in chimpanzees inhabiting Fongoli, a savanna-mosaic habitat at the margins of the chimpanzee range with chimpanzees from Taï National Park, a lowland rainforest centrally located within the West African chimpanzee subspecies ( P. If these habitats are marginal, then we should expect that chimpanzees living in these habitats demonstrate physiological consequences of the extremity of this environment. Savanna-mosaic habitats are thought to represent exceptional circumstances for chimpanzees ( Pan troglodytes), and owing to the virtues of their habitat as well as peripheral biogeographic location, they are often regarded as marginal to the chimpanzee ecological niche. 6Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan, Côte d'Ivoire.5Department of Anthropology, Iowa State University, Ames, IA, United States.4Department of Anthropology, Texas State University, San Marcos, TX, United States.3Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.2German Centre for Integrative Biodiversity Research (iDiv), Leipzig, Germany.1Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.Wessling 1,2 * Tobias Deschner 1 Roger Mundry 3 Jill D.
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