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.
Mayor
Stephen J
SJ
Biology Department, Trent University, 1600 West Bank Drive, Peterborough, ON, K9J 7B8, Canada. jschaefer@trentu.ca
Schaefer
James A
JA
D000818:Animals; D003670:Deer / Q000502:physiology*; D017753:Ecosystem; D011156:Population Density; D012377:Rodentia / Q000502:physiology*; D012589:Sciuridae / Q000502:physiology*