This woodrat is relatively uncommon, yet widely distributed, in northwestern South Dakota. The species probably occurs throughout the rocky areas in the hills and buttes of Harding County, and also frequents abandoned or little-used buildings and feed stations for livestock. All of our specimens were trapped in rocky habitats, but in many such places we trapped unsuccessfully for Neotoma cinerea, even though some sign of its presence frequently was evident. Five of our seven specimens (all taken late in June or early in July) are young of the year in grayish pelage. An adult male trapped on July 14 had testes that measured 14.
Over and Churchill (1945:40) mentioned a specimen, which they referred to the subspecies N. c. cinerea, that "probably came from the Slim Butte area of Harding County." Visher (1914:89) recorded the species as "plentiful and general" in the county.
Microtus ochrogaster haydenii (Baird, 1858)
Prairie Vole
Specimens examined (40).—NE 1/4 sec. 22, R. 1 E, T. 23 N, 1; NW 1/4 sec. 15, R. 5 E, T. 22 N, 1; 2 mi. N, 5 mi. W Ludlow, 4; 4 mi. S, 7 mi. W Ladner, 19; 1/2 mi. W Reva, 2; SW 1/4 sec. 30, R. 7 E, T. 18 N, 3; 10 mi. S, 5 mi. W Reva, 10.
The prairie vole is the most abundant of the three microtines that are known from Harding County. Our specimens came primarily from areas of relatively dense grasses, such as those found in stream bottoms and along fencerows. At two places, along a fencerow 1/2 mi. W Reva and in Deer Draw, 10 mi. S and 5 mi. W Reva, Microtus ochrogaster and the meadow vole, M. pennsylvanicus, were trapped together.
Nine females taken late in May and in June carried an average of 4.4 (3-6) embryos that averaged 14.8 (4-25) in crown-rump length. Each of two lactating females taken in late May had six placental scars. Testes of seven adult males taken in May and June averaged 13.1 (12-16) in length.
Microtus 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.