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Comparison of small mammal communities in a prairie, old field, and farm

Emily Vincent, Michael Britton, Curt Hardacre, Michael Tobin
BIO 345, fall 2013

introduction 

Human development of land dramatically alters the physical appearance of the environment, but effects on local ecosystems are not always known.  Because of its recent land use changes, the DePauw Nature Park is an excellent site to study the effects on land use on ecosystems.  The recent construction of a small farm and the recent restoration of farmland into a small prairie provide sites to study how changes in land use could affect the ecosystems.  We studied the effects of land use changes on small mammal communities at the campus farm, an old field next to the campus farm, and a restored prairie.

The objective of our study was to analyze differences in abundance and diversity of small mammal communities in relation to land use and vegetative cover in the DePauw Nature Park.  We predicted that the restored prairie would have the highest numbers and greatest diversity of small mammals.  We also predicted that the farm would have the lowest numbers and lowest diversity of small mammals.  

methods

We used Sherman traps to capture and release small mammals.  At each site we set up two parallel transects of 12 traps spaced 5 meters apart.  We trapped small mammals on three dates:  October 15, October 29, and November 5.  At each trap site, we estimated plant cover composition using six categories:  tall grasses, medium grasses, short grasses, bare ground, herbaceous plants, and woody plants.

results

We caught four species of small mammals:  meadow jumping mouse (Zapus hudsonius), meadow vole (Microtus pennsylvanicus), white-footed mouse (Peromyscus leucopus), and short-tailed shrew (Blarina brevicauda).  We caught the highest number of individuals in the old field and the lowest number of individuals in the farm.  The composition of the vegetation differed among the three sites.  The farm had 98% short grass or bare ground.  The old field had 61% tall or medium grasses, and the prairie had 66% tall or medium grasses.  

discussion

Capture rates of small mammals were much lower at the farm than in the old field or prairie.  This difference was due to the lack of vegetative cover at the farm and the close proximity of human contact.  Most of the land in the farm is short grasses or bare ground whereas the old field and prairie were covered by mostly tall or medium grasses.  Small mammals are highly dependent on vegetative cover and tend to avoid open areas.  Small mammals were relatively abundant in the old field next to the farm, but the recent conversion of this field to farmland has made it unsuitable habitat for small mammals.  

We expected small mammals to be more abundant and diverse in the prairie, but we observed higher numbers and diversity in the old field.  We are not sure why these results occurred.  Both sites had similar proportions of tall and medium grasses, which provide adequate cover for small mammals.  

If similar studies are conducted in the future, we recommend longer time periods with more transects per site.  We also recommend studies of soil compaction and soil composition.  

Overall, the results of our study imply that vegetative cover and agricultural land use affect the composition of small mammal communities.  The lack of small mammals at the farm implies that this land use conversion has negatively affected the environmental conditions that allow small mammals to survive.