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University of Michigan Biological Station

The University of Michigan Biological Station (UMBS) was founded in 1909.

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Is Global Change Affecting Populations of Small Mammals in Northern MI?

Animal Population
Climate
Fauna
Terrestrial
small mammals
Project Abstract: 
Analysis of historical records of the distributions of a number of small mammal (rodent, shrew, opossum) species strongly suggests a pattern of replacement of northern species by southern species in the northern Great Lakes region. In a few well-studied communities in the Upper Peninsula of Michigan, the commonest species of mammals are now southern invaders like white-footed mice (Peromyscus leucopus) and southern flying squirrels (Glaucomys volans). Much of the change has happened in the last 30 years, a time when climate has warmed substantially and winters have become much shorter. Our goal is to document the extent of the faunal change, and through a combination of long-term monitoring and sampling across a variety of habitats that experience different climatic regimes, test the hypothesis that climate change is responsible. This project involves two activities. The first is a semi-annual census of small mammals carried out at 3 sites at UMBS during the fall and spring of each year. This has been ongoing since 1988. The second involves broad surveys of small mammal communities in northern MI, at the Biological Station (including Sugar Island) and at as many other locations in the region as we can manage.
Investigator(s): 
Philip Myers
Jill C Witt
Investigators: 
pmyers
wittjill
Status of Research Project: 
Active
Related data sets: 
Northern Michigan Rodent Distribution
Small Mammal Census - University of Michigan Biological Station
Years Active: 
2010 to 2027
Research sites: 
Indian Point Hardwoods
UMBS Burn Plots
Reese's Swamp
Methods: 
All sampling is done using livetraps to minimize our impact on small mammal populations. Three census lines were set up in 1988, one each at Indian Point, the Burn Plots, and Reese's swamp. Each line consists of 20 stations. I set 3 livetraps (2 small Sherman traps and 1 large Sherman) at each station, and check them for 2 days and 3 nights in May and September. I record species captured and attributes such as sex, reproductive condition, age, and body mass. The more general survey trapping is done in much the same way, using Sherman livetraps. Locations are chosen based on habitat, accessibility, and history of sampling nearby. This project has three components. First, I use live-trapping techniques to census small mammal populations along three permanent trap lines at the UM Biological Station. I have done this for 24 years, and the records have allowed me to begin to test hypotheses concerning annual variation in common species in northern Lower Michigan. Some strong relationships have emerged, but because of the considerable year-to-year variation in biotic and physical conditions, others that are tantalizingly suggested by the data need confirmation. Second, I conduct survey trapping at sites throughout Michigan to determine the species present and their abundance. These records are compared with historical records (the archives of the UM Museum of Zoology). We have shown that very substantial change in composition has taken place in many communities in northern Michigan. We’re now exploring the correspondence of that change with climate change, but better resolution (survey data from more sites) is needed. Third, we follow the population biology of deer mice and white footed mice at a location in the Pigeon River State Forest, northern Lower Peninsula, where the two occur together. Deer mice have recently (last 30 years) become uncommon in this area (although they remain abundant in the Upper Peninsula) and are apparently being replaced by white-footed mice, a process that may be driven by climate change. Through repeated live-trapping of marked individuals, we hope to gain a better understanding of their reproductive patterns, demographies, use of microhabitats, territoriality, and interspecific interactions through this part of the study.