This study tested the null hypothesis that densities of mammalian populations are constant over patches of varied size. In other words, performance as estimated by density does not covary with patch area. Researchers used a composite database from published studies and found that densities of 20 out of 32 species did not vary with patch area. Five species showed increasing density-area relationships and seven species showed decreasing density-area relationships. Landscapes comprised of smaller, less isolated patched tended to have negative density-area relationships and landscapes with large, more isolated patched tended to have positive density-area relationships. These results indicate that there are no density-area relationships that operate over all systems of patches. Rather, patterns appear to be scale dependent: frequent movement of individuals in the habitat (patch) selection process over smaller-scaled landscapes produced negative density-area relationships. Movement of individuals among more isolated patches appeared to be related to larger and longer-scale population processes involving colonization and extinction and positive density-area relationships.
Conclusions: There are no density-area relationships that operate over all systems of patches. Rather, patterns appear to be scale dependent.