To understand how animals select resources we need to analyze selection at different spatial levels or scales in the habitat. We investigated which physical characteristics of trees (dimensions and structure, e.g., height, trunk diameter, number of branches) determined nesting selection by chimpanzees (Pan troglodytes) on two different spatial scales: individual nesting trees and nesting sites. We also examined whether individual tree selection explained the landscape pattern of nesting site selection. We compared the physical characteristics of actual (N = 132) and potential (N = 242) nesting trees in nesting sites (in 15 plots of 25 m × 25 m) and of all trees in actual and potential nesting sites (N = 763 in 30 plots of 25 m × 25 m). We collected data in May and June 2003 in Issa, a dry and open savanna habitat in Tanzania. Chimpanzees selected both the site they used for nesting in the landscape and the trees they used to build nests within a nesting site, demonstrating two levels of spatial selection in nesting. Site selection was stronger than individual tree selection. Tree height was the most important variable for both nesting site and tree selection in our study, suggesting that chimpanzees selected both safe sites and secure trees for sleeping.

中文翻译：

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决定睡觉的地方：生活在坦桑尼亚伊萨大草原的黑猩猩（Pan troglodytes）筑巢选择的空间水平

要了解动物如何选择资源，我们需要分析栖息地中不同空间水平或尺度的选择。我们调查了树木的哪些物理特征（尺寸和结构，例如高度、树干直径、树枝数）决定了黑猩猩（Pan troglodytes）在两个不同空间尺度上的筑巢选择：个体筑巢树木和筑巢地点。我们还检查了个别树木的选择是否解释了筑巢地点选择的景观模式。我们比较了筑巢地点（15 个 25 m × 25 m 的地块）中实际（N = 132）和潜在（N = 242）筑巢树木的物理特征以及实际和潜在筑巢地点（N = 763 in 30 个 25 m × 25 m 的地块）。我们于 2003 年 5 月和 6 月在坦桑尼亚干燥开放的热带稀树草原栖息地伊萨收集了数据。黑猩猩既选择了它们在景观中筑巢的地点，又选择了它们用来在筑巢地点筑巢的树木，这表明筑巢有两个层次的空间选择。站点选择比单个树选择强。在我们的研究中，树高是筑巢地点和树木选择的最重要变量，这表明黑猩猩选择安全地点和安全树木睡觉。