Michigan Rodents Distribution at the University of Michigan Biological Station, Pellston, MI, from 1883 to 2007

Distribution of rodents in northern Michigan documented by Dr. Phil
Myers, et al. We use museum and other collection records to document large and
extraordinarily rapid changes in the ranges and relative abundance of
9 species of mammals in the northern Great Lakes region (white-footed
mice, woodland deer mice, southern red-backed voles, woodland jumping
mice, eastern chipmunks, least chipmunks, southern flying squirrels,
northern flying squirrels, common opossums). These species reach
either the southern or the northern limit of their distributions in
this region. Changes consistently reflect increases in species of
primarily southern distribution (white-footed mice, eastern chipmunks,
southern flying squirrels, common opossums) and declines by northern
species (woodland deer mice, southern red-backed voles, woodland
jumping mice, least chipmunks, northern flying squirrels).
White-footed mice and southern flying squirrels have extended their
ranges over 225 km since 1980, and at particularly well-studied sites
in Michigan's Upper Peninsula, small mammal assemblages have shifted
from numerical domination by northern species to domination by
southern species. Repeated re-sampling at some sites suggests that
southern species are replacing northern ones rather than simply being
added to the fauna. Observed changes are consistent with predictions
from climatic warming but not with predictions based on recovery from
logging or changes in human populations. Because of the abundance of
these focal species (the 8 rodent species make up 96.5% of capture
records of all forest-dwelling rodents in the region and 70% of
capture records of all forest-dwelling small mammals) and the
dominating ecological roles they play, these changes substantially
affect the composition and structure of forest communities. They also
provide an unusually clear example of change that is likely to be the
result of climatic warming in communities that are experienced by
large numbers of people.