The ten species of mammals listed below are not known certainly to occur in Harding County, but there is a strong likelihood that some will be found in the area or once occurred there. Three were mentioned by Visher (1914) as having been seen or taken in the county at the time of, or prior to, his biological survey of 1910 and 1912, but his accounts were not supported by adequate documentation. In addition to the kinds listed, several other mammals, such as Keen's bat (Myotis keenii septentrionalis), the red bat (Lasiurus borealis borealis), or the least weasel (Mustela nivalis campestris) are known to occur near enough to the area that the possibility of their presence cannot be discounted.
Sorex cinereus haydeni Baird, 1858.—No shrews presently are known from Harding County. This species almost certainly will be found in relatively mesic habitats there, however, as our field parties have taken specimens in adjacent Bowman County, North Dakota, and only a few miles to the west of the county in the Long Pines Hills of Montana.
Sorex merriami merriami Dobson, 1890.—This shrew inhabits somewhat more xeric areas than most other members of the genus and surely occurs in northwestern South Dakota. Specimens are on record from western North Dakota and northwestern Nebraska, and in the summer of 1970 a field party from The University of Kansas took one but a half mile west of the Harding County (state) line in Carter County, Montana.
Spermophilus richardsonii richardsonii (Sabine, 1822).—Visher (1914:88) reported that he saw individuals of this species "in the extreme northwestern corner" of Harding County. However, the limits of the presently known range of the species are approximately 150 miles distant from that area.
Sciurus niger rufiventer E. Geoffroy St.-Hilaire, 1803.—The fox squirrel presently is unrecorded from much of the West River part of South Dakota. Hoffmann et al. (1969:589), however, recently have reported specimens from along the Yellowstone River in eastern Montana and this squirrel now may occur also along the Little Missouri River. It was not surprising, therefore, when residents of Camp Crook reported to us that in recent years they have seen what were believed to be fox squirrels along the Little Missouri near that town. Specimens now are needed to verify these reports.
Lagurus curtatus pallidus (Merriam, 1888).—The sagebrush vole undoubtedly occurs, albeit probably uncommonly, in areas of sage in northwestern Harding County, because specimens have been taken recently a few miles north and west of the county in North Dakota and Montana, respectively. We trapped unsuccessfully (900 trap nights) for this vole on sage flats to the north of Camp Crook and west of the Little Missouri River in the summer of 1970. "Sign," which appeared to be that of Lagurus, was found in this area, but only Peromyscus maniculatus and Spermophilus tridecemlineatus were trapped there.
Rattus norvegicus (Berkenhout, 1769).—No records of this introduced murid are available from northwestern South Dakota, but it seems likely that the species has reached the area.
Vulpes velox (Say, 1823).—Visher (1914:90) reported seeing a swift fox "along the Little Missouri Valley in North Dakota" and further noted that an early settler [Sol Catron] had "trapped a few" in Harding County. Whatever the former status of this fox in northwestern South Dakota may have been, the species evidently does not occur in the area today, or is rare, and the subspecific status of V. velox throughout much of the Northern Great Plains is in question. A specimen obtained in February of 1970 at a place 9 mi. N and 2 mi. E Scranton, Slope Co., North Dakota, is the only swift fox taken north of Nebraska in recent years (Pfeifer and Hibbard, 1970:835).
Urocyon cinereoargenteus ocythous Bangs, 1899.—Jones and Henderson (1963:288) reported a gray fox from Deer Ear Buttes, Butte Co., South Dakota, approximately 15 miles south of the Harding County line. This species appears to have dispersed westward in recent years, and its future occurrence in the county is likely.
Gulo gulo luscus (Linnaeus, 1758).—The wolverine probably occurred sparingly in northwestern South Dakota until the time of early settlement, but we know of no verified records from Harding County or surrounding areas. A recent report of a specimen taken south of Timber Lake, Dewey Co., South Dakota (Jones, 1964:283), indicates that it may again be found in the area.