Primates are sometimes categorized in terms of their habitat. Although such categorization can be oversimplistic, there are scientific benefits from the clarity and consistency that habitat categorization can bring. Chimpanzees (Pan troglodytes) inhabit various environments, but researchers often refer to “forest” or “savanna” chimpanzees. Despite the wide use of this forest–savanna distinction, clear definitions of these landscapes for chimpanzees, based on environmental variables at study sites or determined in relation to existing bioclimatic classifications, are lacking. The robustness of the forest–savanna distinction thus remains to be assessed. We review 43 chimpanzee study sites to assess how the landscape classifications of researchers fit with the environmental characteristics of study sites and with three bioclimatic classifications. We use scatterplots and principal components analysis to assess the distribution of chimpanzee field sites along gradients of environmental variables (temperature, rainfall, precipitation seasonality, forest cover, and satellite-derived Hansen tree cover). This revealed an environmental continuum of chimpanzee study sites from savanna to dense forest, with a rarely acknowledged forest mosaic category in between, but with no natural separation into these three classes and inconsistencies with the bioclimatic classifications assessed. The current forest–savanna dichotomy therefore masks a progression of environmental adaptation for chimpanzees, and we propose that recognizing an additional, intermediate “forest mosaic” category is more meaningful than focusing on the ends of this environmental gradient only. Future studies should acknowledge this habitat continuum, place their study sites on the forest–savanna gradient, and include detailed environmental data to support further attempts at quantification.

中文翻译：

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在非洲大尺度环境梯度中对黑猩猩（Pan troglodytes）景观进行分类

灵长类动物有时根据栖息地进行分类。尽管这种分类可能过于简单，但栖息地分类带来的清晰性和一致性在科学上是有益的。黑猩猩（Pan troglodytes）栖息在各种环境中，但研究人员经常提到“森林”或“稀树草原”黑猩猩。尽管这种森林 - 稀树草原的区别被广泛使用，但基于研究地点的环境变量或根据现有生物气候分类确定的黑猩猩这些景观的明确定义仍然缺乏。因此，森林-稀树草原区分的稳健性仍有待评估。我们审查了 43 个黑猩猩研究地点，以评估研究人员的景观分类如何与研究地点的环境特征和三种生物气候分类相适应。我们使用散点图和主成分分析来评估沿环境变量（温度、降雨量、降水季节性、森林覆盖率和卫星衍生的汉森树覆盖率）梯度的黑猩猩野外站点的分布。这揭示了从稀树草原到茂密森林的黑猩猩研究地点的环境连续体，中间有一个很少被承认的森林镶嵌类别，但这三个类别没有自然分离，并且与评估的生物气候分类不一致。因此，当前的森林-稀树草原二分法掩盖了黑猩猩环境适应的进展，我们建议认识到一个额外的中间“森林马赛克”类别比只关注这种环境梯度的末端更有意义。