The Mammals of Warren Woods, Berrien County, Michigan Part 2

_Microtus pennsylvanicus pennsylvanicus._ Pennsylvania vole. 5.

A large ravine south of the river had been cleared of trees evidently several years previously, and it has now grown up mostly to sedges, gra.s.s, and iris in its more moist parts. Along the little brook which flows through the ravine there is a fringe of willows, and among the sedges a number of shrubs and small trees occur, mostly thorns and a few young sycamores and black walnuts.

Fifty mouse traps set in this habitat took on the first day, August 16, three northern white-footed mice and three Pennsylvania voles.

More voles and a short-tailed shrew were taken on later days.

_Cleared-upland rush habitat_:

_Mephitis nigra._ Eastern skunk. Den.

_Peromyscus maniculatus bairdii._ Prairie white-footed mouse. 1.

_Synaptomys cooperi._ Cooper lemming-vole. 1.

_Microtus pennsylvanicus pennsylvanicus._ Pennsylvania vole. 7.

_Microtus ochrogaster._ Prairie vole. 1.

_Citellus tridecemlineatus tridecemlineatus._ Thirteen-striped ground squirrel. 2.

In the shallow, poorly drained depressions of the cleared upland the vegetation is dominated by rushes, which grow in clumps and form a thick growth, reaching a height of about one meter as a maximum. At the edges of the habitat and in places not thickly covered by the rushes a growth of sedges, gra.s.ses, and moss covers the ground; but under the thickest growth of rushes the ground is bare and is evidently covered by water during a part of the year. On this upland one small pond surrounded by rushes did not dry up until late in August. In a few places small blackberry thickets occur in the areas of rushes and dominate all other plants.

Fifty traps set in this habitat, on August 8, took on the first night one prairie white-footed mouse and one Pennsylvania vole; the prairie white-footed mouse was taken just at the edge of the growth of rushes.

Other Pennsylvania voles as well as a lemming-vole, a prairie vole, and several young ground squirrels were secured on later nights by the same trap-line. A skunk den was situated in a blackberry thicket in the midst of the largest patch of rushes.

_Cleared-upland sedge habitat_:

_Peromyscus maniculatus bairdii._ Prairie white-footed mouse. 3.

_Microtus pennsylvanicus pennsylvanicus._ Pennsylvania vole. 1.

_Microtus ochrogaster._ Prairie vole. 9.

_Mus musculus musculus._ House mouse. 1.

_Citellus tridecemlineatus tridecemlineatus._ Thirteen-striped ground squirrel. Burrows.

Sedges are dominant over a part of the cleared upland, occurring on the moist gentle slopes which are too well drained for rushes, but not in any numbers on the drier and higher parts of the upland. With the sedges there are a few gra.s.ses, and the ground is sometimes covered by a moss, but the sedges are by far the most abundant plant.

Fifty mouse traps set in this habitat took on the first night, August 15, one prairie white-footed mouse and one prairie vole. Other prairie voles and white-footed mice were taken on later nights, as well as one Pennsylvania vole and one house mouse. Burrows of the thirteen-striped ground squirrel were numerous in the sedges.

_Cleared-upland blue-gra.s.s habitat_:

_Peromyscus maniculatus bairdii._ Prairie white-footed mouse. 12.

_Mus musculus musculus._ House mouse. 1.

_Citellus tridecemlineatus tridecemlineatus._ Thirteen-striped ground squirrel. 23.

The most widespread habitat of the cleared upland on the south part of the preserve is the blue-gra.s.s habitat. In this habitat the blue-gra.s.s, _Poa_, is the dominant plant, growing to a height of usually not over 0.5 meter. With the blue-gra.s.s are a.s.sociated a few thistles, yarrow, and several other herbs. During the whole period of my stay in the region, July and August, the habitat was very dry, and the gra.s.s and herbs had mostly dried up. This habitat and all the other habitats of the clearing were being heavily pastured by stock.

Trap-lines totaling one hundred mouse traps, set on August 6 and August 18, took on the first nights two prairie white-footed mice, one house mouse, and one young thirteen-striped ground squirrel. More white-footed mice were taken on later nights. Many ground squirrels were taken in larger traps at the mouths of their burrows; most of these were young of the year, and all of them were very fat in preparation for their approaching hibernation.

_Cultivated field habitat_:

_Scalopus aquaticus machrinus._ Prairie mole. 1.

_Peromyscus maniculatus bairdii._ Prairie white-footed mouse. 23.

_Microtus ochrogaster._ Prairie vole. 1.

_Mus musculus musculus._ House mouse. 2.

_Sylvilagus florida.n.u.s mearnsii._ Mearns cottontail. 2.

Cultivated fields occur throughout the region about the woods, but the only ones in which trapping was done were wheat stubble-fields. After the wheat was cut off these stubble-fields grew up rather thickly to weeds. On the ground there were a number of fallen heads of wheat and some sh.e.l.led-out grain, furnis.h.i.+ng abundant food for mice.

Seventy mouse traps set in a wheat stubble-field just north of Warren Woods, caught on the first nights, August 13 and August 29, sixteen prairie white-footed mice. Other white-footed mice and two house mice were taken on later nights. Several cottontails were seen in this field, and a few mole ridges were noted. A prairie mole was taken by Clifford Reid in a gra.s.sy patch at the edge of a garden. In another wheat field the Helming boys picked up a prairie vole.

_Orchard habitat_:

_Peromyscus leucopus noveboracensis._ Northern white-footed mouse. 1.

_Microtus pennsylvanicus pennsylvanicus._ Pennsylvania vole. 2.

No especial study of the mammal life of the orchard was made, and no intensive trapping was done in the habitat. However, the orchard cannot be included in any of the other habitats recognized in the region.

A northern white-footed mouse was caught alive by the Helming boys in an orchard on July 16. A vole was seen to cross a road in a small orchard on July 15; a trap was set and two Pennsylvania voles secured, one a young of the year.

_Edificarian habitat_:[1]

_Blarina brevicauda talpoides._ Short-tailed shrew. 1.

_Peromyscus leucopus noveboracensis._ Northern white-footed mouse. 2.

_Rattus norvegicus._ Norway rat. 4.

_Mus musculus musculus._ House mouse. 22.

_Sylvilagus florida.n.u.s mearnsii._ Mearns cottontail. 2.

From time to time a few traps were set in the old farmhouse and in the barn and other outbuildings of our camp. In these buildings northern white-footed mice, Norway rats, and house mice were taken. Several cottontails were seen in and under the old barn. The Helming boys trapped a short-tailed shrew and also house mice and a white-footed mouse in the bas.e.m.e.nt of their house.