life on the edge : the role of habitat selection on vole density near forest boundaries
abstract
theories of density-dependent habitat selection predict pronounced gradients of
population density near habitat edges. population density in high-quality habitats
should decline toward edges with lower-quality habitats, and population density in
low-quality habitats should increase toward boundaries with higher-quality habitats.
this pattern should be more obvious near abrupt boundaries than near ecotones where
habitats gradually grade one into the other. 1 tested the predictions using the density
of red-backed voles (clethrionomys gapperi) along eight belt transects crossing edges
between natural and anthropogenic boreal forest habitats in northwestern ontario.
transects were classified as having either a gradual (70 m to 90 m ecotone) or abrupt
edge (20m ecotone). vole density varied consistently between pairs of habitats, but
there was no detectable gradient in density at either abrupt or gradual edges. the
absence of an edge effect may be related to errors in the assessment of habitat quality
by individuals confronted with a matrix of patch types near edges separating similar
habitats. another possibility is that an, as yet, unidentified agent or process alters the
quality of red-backed vole habitats near boreal-forest edges.
collections
- retrospective theses [1604]