The many faces of population density.
Population density, one of the most fundamental demographic attributes, may vary systematically with spatial scale, but this scale-sensitivity is incompletely understood. We used a novel approach-based on fully censused and mapped distributions of eastern grey squirrel (Sciurus carolinensis) dreys, beaver (Castor canadensis) lodges, and moose (Alces alces)--to explore the scale-dependence of population density and its relationship to landscape features. We identified population units at several scales, both objectively, using cluster analysis, and arbitrarily, using artificial bounds centred on high-abundance sites. Densities declined with census area. For dreys, this relationship was stronger in objective versus arbitrary population units. Drey density was inconsistently related to patch area, a relationship that was positive for all patches but negative when non-occupied patches were excluded. Drey density was negatively related to the proportion of green-space and positively related to the density of buildings or roads, relationships that were accentuated at coarser scales. Mean drey densities were more sensitive to scale when calculated as organism-weighted versus area-weighted averages. Greater understanding of these scaling effects is required to facilitate comparisons of population density across studies.
Biology Department, Trent University, 1600 West Bank Drive, Peterborough, ON, K9J 7B8, Canada. jschaefer@trentu.ca
Stephen J
SJ
Mayor
James A
JA
Schaefer
D000818:Animals; D003670:Deer / Q000502:physiology*; D017753:Ecosystem; D011156:Population Density; D012377:Rodentia / Q000502:physiology*; D012589:Sciuridae / Q000502:physiology*