Date of Award
Doctor of Philosophy (PhD)
Dr . John J. Christian
Dr. Stuart 0. Landry
Dr. Donald R. Coates
Mammal populations -- Vermont -- Rutland County; Mammal populations -- New York (State) -- Washington County; Habitat selection; Animal ecology
Previous trapping in the slate belt, including both Rutland County, Vermont, and Washington County, New York, has indicated a relative paucity of small mammalian species. There are also rather low populations levels of those mammals present when compared to other regions in Vermont and nearby states. The evolution of the soils from the slate bedrock seems to be the key to understanding the problem of species exclusion from the region.
The bedrock of the region is part of the Taconic sequence of rocks, and is primarily slate and phyllite that ranges in age from Early Cambrian to Middle Ordovician. The lithology of the Taconic bedrock is largely responsible for the type of soil development in the slate belt. Shallow soils with both large and small slate fragments have been derived from the glaciated slates and shales of the bedrock. Typically, the soils of the slate belt have developed to a depth of less than 0.6 m. The members of the Gray-Brown Podzolic soil province typically lack a well developed humus layer, and instead, raw organic material is found in the surface layer. The effects of intensive sheep grazing during the 19th century are still to be seen in the very thin topsoil, and loss of most humus from the soils of the region.
To determine the numbers and types of small mammals present, trap-sites were chosen to maximize the different types of habitats 181 containing different combinations of environmental factors. Habitats were divided into five main categories, and the type of cover at each trap was recorded. Species trapped included Peromyscus Zeucopus noveboracensis, Peromyscus maniculatus gracilis, Sorex fumeus, Blarina brevicavda, Clethrionomys gapperi, Napaeozapus insignis, Condylura cristata, Zapus hudsonius, Microtus pennsylvanicus, and Tamias striatus. The capture rate was 25.00 animals per 1000 trap-nights (222 animals in 8880 trap-nights). Various conclusions are drawn concerning the occurrence of different species and various factors, including type of soil, type of bedrock, and type of cover. Eight species of small mammals known to occur in the nearby regions could not be trapped in the slate belt. They include Sorex cinereus, Sorex dispar, Microsorex hoyi, Sorex palustris, Parascalops breweri, Microtus chrotorrhinus, Pitymys pinetorum, and Synaptomys cooperi.
It is concluded that the shallow depth to bedrock, abundance of slate fragments in the upper soil profile, and weakly developed humus layer are probably detrimental to burrowing species of small mammals. The lack of a proper substrate, e.g. talus, is of immediate importance to some species of small mammals, and the lack of this formation directly excludes them from the region.
Berkowitz, Albert Stanley, "Lithologic, edaphic, and biotic factors of small mammal habitats in the slate belt of Western Rutland County, Vermont, and Eastern Washington County, New York" (1976). Graduate Dissertations and Theses. 105.