crotus pennsylvanicus insperatus~ (J. A. Allen, 1894)

Meadow Vole

_Specimens examined_ (14).--1/2 mi. W Reva, 1; 10 mi. S, 5 mi. W Reva,
12; 7 mi. S, 4-1/2 mi. E Harding, 1.

This vole evidently is limited in Harding County to habitats of dense
grass and forbs adjacent to water. We failed to trap the species in some
areas that appeared to be suitable for occupancy.

Two females, collected on May 15 and June 2, contained three and six
embryos, respectively, that measured 15. One female with five placental
scars (May 15) and two with six (May 16, June 2) also were trapped, and
a lactating female was captured on June 20. Testes of two adult males
taken in spring (May 18 and June 2) measured 15, and those of one
weighing 45.6 grams that was taken early in June measured 17.

~Ondatra zibethicus cinnamominus~ (Hollister, 1910)

Muskrat

The muskrat is common in Harding County. Half a century ago Visher
(1914:89) noted that it was "Fairly plentiful along the streams having
deep permanent 'holes'."

Seven adults, all in winter pelage, were taken late in March from a pond
near the west side of Slim Buttes (5 mi. S and 14 mi. E Buffalo). Testes
of three adult males measured 17, 19, and 22; of three females, none
evidenced reproductive activity.

~Mus musculus~ Linnaeus, 1758

House Mouse

The house mouse evidently is uncommon in rural environments in
northwestern South Dakota. One subadult female was trapped along a
"weedy" fencerow, 2 mi. N and 5 mi. W Ludlow.

~Zapus hudsonius campestris~ Preble, 1899

Meadow Jumping Mouse

Eleven specimens of this jumping mouse were taken from a relict
population restricted to a shrub-grass habitat adjacent to a small
spring-fed stream and impoundment in Deer Draw (10 mi. S and 5 mi. W
Reva). Similar isolated populations may be present in the few other
suitable mesic habitats in Harding County, but we have trapped
extensively, yet unsuccessfully, for _Zapus_ in such situations;
specimens are known, however, from the Long Pine Hills and from along
the Little Missouri River in adjacent Carter County, Montana. It is of
interest that a relict population of _Peromyscus leucopus_ also occurs
in Deer Draw.

The testes of two adult males obtained on June 3 measured 7, whereas
those of one taken on May 16 measured 16. Seven embryos (measuring 8 in
crown-rump length) were carried by a molting female trapped on June 16.
Our specimens of _Zapus_, currently under study by Paul B