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."
[Illustration: FIGURE 1. Range of the Prairie Vole (_Microtus
ochrogaster_).]
Several early naturalists in this country commented on the fluctuations
in numbers of individuals, and on the breeding and feeding habits of
voles. Kennicott (1857) in an agricultural report on the mammals of
Illinois wrote about the breeding of the prairie vole. He described its
stores of plants and commented on the behavior of some captives. Quick
and Butler (1885) discussed the habits of _Microtus ochrogaster_ as
well as those of _M. pennsylvanicus_, _Pitymys pinetorum_, and
_Synaptomys cooperi_ in Indiana, and described the feeding and breeding
habits of these species. Criddle (1926) gave an account of the feeding
and breeding habits of _Microtus ochrogaster_ in Manitoba, and Fisher
(1945) published a short description of the food and reproduction of the
same species as he observed it in Missouri. Stone investigated the fauna
in the nests of this vole in the same state, but has not yet, as of
March, 1946, published his findings.