| PAGE | |
| Introduction | [128] |
| Methods | [130] |
| Molt | [131] |
| Food and Habitat | [132] |
| Types of cover | [132] |
| Cuttings | [133] |
| Food caches | [134] |
| Plants used as food and as cover | [135] |
| Associates | [137] |
| Nest and Burrows | [137] |
| External Parasites | [138] |
| Fleas (Siphonaptera) | [139] |
| Lice (Anoplura) | [141] |
| Mites (Acari except Ixodoidea) | [142] |
| Ticks (Ixodoidea) | [143] |
| Reproduction | [144] |
| Age classes | [144] |
| Fecundity | [144] |
| Size of litters | [146] |
| The breeding season | [147] |
| Summary | [149] |
| Literature Cited | [150] |
INTRODUCTION
The prairie vole (Microtus ochrogaster) at Lawrence, Kansas, is approximately 5-1/2 inches in length, of which the tail comprises 1-1/4 inches, and weighs approximately 1-1/2 ounces. The color on the dorsum is dark gray with a grizzled appearance from the mixture of black and fulvous on the long hairs; the venter is paler, sometimes pale fulvous or cinnamon. The animal is compactly built much as are the other microtine rodents. The short legs and short tail, small eyes and partly hidden ears, and heavy and flattened head all suggest its semifossorial mode of life. The prairie vole spends most of its time in an elaborate system of tunnels (some entirely below the ground) and in almost hidden galleries in the dense grass.
Microtus ochrogaster can be separated from other voles in its geographic range by a combination of several characters. The plantar tubercles usually number five, although a few individuals with six tubercles were found at Lawrence, Kansas. Microtus pennsylvanicus, normally with six plantar tubercles, as Bole and Moulthrop (1942:156) pointed out, sometimes has only five. Therefore, the number of plantar tubercles alone is not a certain means for separating pennsylvanicus from ochrogaster. The color of the venter of ochrogaster is usually fulvous or cinnamon instead of grayish as in pennsylvanicus, but there is variation in this respect too; some prairie voles also have a grayish venter. The shorter tail of ochrogaster will assist in establishing its identity where it occurs with pennsylvanicus. The third upper molar has two closed triangles in ochrogaster and usually three in pennsylvanicus. The pelage of ochrogaster is coarse whereas pennsylvanicus has fine fur. Prairie voles may be separated from pine mice (Pitymys nemoralis and P. pinetorum) with which they are sometimes found, by the larger eyes, less rusty color, and longer tail. The Cooper lemming mouse (Synaptomys cooperi) differs from the prairie vole in having the upper incisors grooved, and in possessing a shorter tail which approximates the hind foot in length.
Of Microtus ochrogaster from Lawrence, Douglas County, Kansas, average measurements of twenty-five adult males are: total length, 143 (121-167) mm.; tail, 32 (25-42) mm.; hind feet, 20 (17-22) mm.; weight, 43 (38-55) grams. Twenty-five adult females from the same place average: total length, 150 (131-170) mm.; tail, 33 (31-41) mm.; hind foot, 19 (17-21) mm.; weight, 45 (38-58) grams.
The prairie vole is found in suitable habitats in the central part of North America. It has been recorded from Edmonton, Alberta, in the northwest (Bailey, 1900:76), southeastward to Chesapeake, Ohio (Bole and Moulthrop, op. cit.:156), and in the southwest as far as Ft. Reno, Oklahoma (Bailey, op. cit.:74). See [figure 1] showing the known range of Microtus ochrogaster. Microtus ludovicianus, a close relative of ochrogaster, has been taken along the southern part of the boundary between Texas and Louisiana (Lowery, 1943:247).
The activities of voles, especially those of the genus Microtus, attracted the attention of naturalists even in early times. Aristotle (translated by Thompson, 1910) wrote: "The rate of propagation of field mice in country places, and the destruction that they cause, are all beyond telling. In many places their number is so incalculable that but very little of the corn-crop is left to the farmer; and so rapid is their mode of proceeding that sometimes a small farmer will one day observe that it is time for reaping, and on the following morning, when he takes his reapers afield, he finds his entire crop devoured. Their disappearance is unaccountable: in a few days not a mouse will be there to be seen."