Geography Reference
In-Depth Information
from black bears and spotted skunks to Pacii c jumping mice and the odd
shrew- mole.
As with our bird studies, we discovered that the variety of mammals
peaked in suburban and exurban landscapes where forest patches were mod-
erately sized (50-150 acres). The diversity of the ground vegetation seemed to
enhance mammal diversity, so that in residential settings even substantial
patches of forest (up to 2,500 acres large) maintained rich communities, as did
small (5-acre) forests in the sparsely peopled exurbs. In extensive forest be-
yond subirdia, the variety of mammals we caught was a bit lower, and in all
but the largest urban forest patches it was substantially lower.
Although the form of the relationship between urbanization and mam-
mal variety paralleled that which we found for birds, the composition of
mammal and bird communities was distinctly dif erent. We observed a mix of
native bird species from young and mature forests and from grassland, tundra,
and meadow, which increased suburban diversity, whereas the mammals of
subirdia drew their variety from nonnative species. There were six species of
native mouse, shrew, weasel, squirrel, and shrew-mole and an equal number
that were invaders: opossum, cat, dog, eastern gray squirrel, raccoon, and rat.
Urban mammal communities also consisted equally of native and nonnative
faunas. In contrast, the mammals of large and wild forests were nearly exclu-
sively native species, with only one nonnative, the ubiquitous eastern gray
squirrel.
The small mammals of Seattle respond to urbanization a bit dif erently
from the mammals of Ohio and Argentina. In Ohio, diversity also peaked in
suburban settings—neighborhoods and golf courses—but it was composed
almost exclusively of native mammals, including shrews, voles, mice, rac-
coons, and opossums. In contrast to the i ndings from Seattle and Ohio, ro-
dent diversity steadily declined in Argentina from a rich costal forest reserve
through parklands and shantytowns to the industrial center of Buenos Aires.
There, nonnative species also buoyed urban mammal diversity, as in Seattle,
