Changes in Small Mammal Communities

Allison Poor; Dr. Phil Myers, University of Michigan; Dr. Barb Lundrigan, Michigan State University

2002-2004

Previous studies of small mammal communities at the Hurons, from the 1940s and 1970s, provided an unusual opportunity to quantitatively assess changes in species' presence and abundance. For her M.S. Thesis, Allison Poor (working with advisors Phil Myers and Barb Lundrigan) replicated the earlier studies. Her results document some large changes in community composition, including, for several taxa shifts from more northern to more southern species. Allison's thesis was successfully defended in 2006. .

A collection of Peromyscus (deer mice), one of the genera showing shifts in dominance. Photo by Allison Poor

The Huron Mountain Club in Marquette County lies close to the distributional limits of a number of mammal species.  Therefore, distributional shifts of these species resulting from global climate change should be readily apparent in the Huron Mountain region.  In the summer of 2004, I conducted a survey of the small terrestrial mammals of the Huron Mountain Club, with the goal of comparing my findings to the results of earlier surveys done in 1947 and 1974.   I trapped with medium Sherman live traps in seven 10 X 12 grids and eight linear transects, and with pitfall traps.  I captured every species that was captured in the earlier surveys, with the exceptions of Sorex hoyi, the pygmy shrew, and Glaucomys sabrinus, the northern flying squirrel.  Glaucomys sabrinus, as well as Glaucomys volans, the southern flying squirrel, and been common the year before; the reason for their absence in 2004 is unknown.  I trapped many white-footed mice, Peromyscus leucopus, which had been absent from the region before 2003, and many eastern chipmunks (Tamias striatus), which now seem to have surpassed least chipmunks (Tamias minimus) in abundance.  These two changes, involving species with historically more southern ranges either spreading at their northern borders or becoming locally more abundant than their boreal counterparts, suggest that global warming may play a role in determining the community composition of the Huron Mountain region.  Another summer of field work is planned, with an additional round of trapping on the same plots, more intense pitfall trapping, and a survey of bat species.