|Title||An analysis of some physical factors affecting the local distribution of the shorttail shrew (Blarina brevicauda hirtlandi) in northern lower Michigan|
|Year of Publication||1952|
|Degree||Doctor of Philosophy|
|Number of Pages||106 pp.|
|University||University of Michigan|
|City||Ann Arbor, MI|
1. On a series of five study areas in northern Lower Michigan, illustrating the main forest associations and soil types of the region, physical conditions (soil moisture, temperature, freezing, and penetrability) of the environment of Blarina brevicauda were recorded and analyzed for a period of 14 consecutive months. 2. This analysis shows that the areas called the Burn, Aspens, Pines, Hardwoods, and Bog stand in that relation to one another in a series with increasing stability of soil temperature. In regard to depth and amount of winter freezing the relation is Burn, Aspen, Pines, Bog, and hardwoods, in decreasing amounts. 3. This analysis shows that the Burn, Aspens, Pines, Bog, and Hardwoods stand in that relation to one another as regards year-round presence of available soil moisture. 4. Quadrat trapping (approximately 4,000 trap-nights) has shown that, at the time of trapping, Blarina is not present on the Burn, rarely in the Aspen, occasionally in the Pines, regularly in the Bog, and in great numbers in the Hardwoods. In contrast, Peromyscus leucopus is present on all areas, but in almost reverse concentration. Citellus tridecemlineatus was found only on the Burn and Aspens, Napaeozapus insignis only in the Hardwoods and Bog, and Sorex cinereus only in the Bog. 5. Because of these relationships, it is postulated that in this region Blarina has a major center of population in the hardwoods areas (loams), with a minor center in coniferous swamps and bogs (peats, mucks, or wet sands), and is present in the dry sandy uplands only to the extent that winter freezing and excessive summer heat and dryness of soil allow it. As succession proceeds and changes in the soil and humus environment occur, Blarina keeps pace by invading the newly accessible areas.