Olfelt, D.R. 1984. Small mammals of reclaimed mine waste in northern Minnesota. Final report submitted to the Minnesota Department of Natural Resources. Unpaged.
The objective of this study was to gain insight into the response of small mammals to a revegetated taconite tailings basin. To achieve this, the following was goals were implemented: 1) learn which small mammals species were present on the tailings basin, 2) discover the relative abundance of those species, and 3) determine what factors in the environment of the tailings basin affect species distribution. This paper outlines the work done and inferences drawn by the author to date.
Five 700 m long sampling transects were established on a tailings basin (National Steel Pellet Company's taconite tailings basin at Keewatin, Minnesota). The location of each transect was chosen subjectively in an attempt to encompass the range of habitat types present on the basin. Snap-traps baited with a mixture of peanut butter, oatmeal and anise oil were placed along each transect. Two trapping bouts, June 24-27 and August 11-14 were conducted, for a total of 2800 twenty-four hour trap nights. The habitat variable data collected along each transect was averaged to yield a single, transect value for each variable. These values were then used to infer habitat preferences of the small mammals.
A total of 93 small mammals were captured in 2800 trap nights. 59% were Microtus pennsylvanicus and 26% were Peromyscus maniculatus gracilis. Four other species were caught but in very small numbers. Microtus were caught primarily in transects characterized by coarse, grassy cover and litter. Peromyscus were most abundant in the "Plantation" and "Deadwood" transects. Microtus appear to prefer substrates with intermediate particle size and moisture. Peromyscus were found in areas with bare ground, both high and relatively low sapling densities, and at either end of the substrate moisture/particle size gradient. Both the abundance and diversity of small mammals is lower on the tailings basin than has been recorded in natural habitats in the area (Batten 1980). Low species diversity and abundance are an indication that the habitat needs of small mammals are not being fully met by the revegetated tailings basin. In general, deer mice have been most successful at colonizing these mine wastes, managing to live in areas with scarcely any vegetation. Rock stockpiles seem capable of supporting large and, with time, relatively diverse small mammal communities, even without reclamation efforts. The tailings basins need more, and perhaps more diverse, vegetation before they can provide adequate small mammal habitat.