Resampling method for applying density-dependent habitat selection theory to wildlife surveys

Isodar theory can be used to evaluate fitness consequences of density-dependent habitat selection by animals. A typical habitat isodar is a regression curve plotting competitor densities in two adjacent habitats when individual fitness is equal. Despite the increasing use of habitat isodars, their application remains largely limited to areas composed of pairs of adjacent habitats that are defined a priori. We developed a resampling method that uses data from wildlife surveys to build isodars in heterogeneous landscapes without having to predefine habitat types. The method consists in randomly placing blocks over the survey area and dividing those blocks in two adjacent sub-blocks of the same size. Animal abundance is then estimated within the two sub-blocks. This process is done 100 times. Different functional forms of isodars can be investigated by relating animal abundance and differences in habitat features between sub-blocks. We applied this method to abundance data of raccoons and ...生境等密度线理论（Isodar theory）可用于评估动物密度依赖型生境选择所产生的适合度后果。典型的生境等密度线（isodar）是一条回归曲线，用于描绘个体适合度相等时，两个相邻生境中的竞争者密度。尽管生境等密度线的应用愈发广泛，但其适用范围仍主要局限于预先明确划定的成对相邻生境区域。我们开发了一种重采样方法，可利用野生动物调查数据在异质性景观中构建生境等密度线，无需预先定义生境类型。该方法的具体流程为：在调查区域内随机布设区块，并将每个区块均分为两个尺寸一致的相邻子区块；随后对两个子区块内的动物种群丰度进行估算，该流程重复执行100次。通过关联动物丰度与子区块间的生境特征差异，可对多种函数形式的生境等密度线进行研究。我们将该方法应用于浣熊及……的种群丰度数据中。