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