One adult male examined for ectoparasites harbored a tick, _Dermacentor andersoni_ Stiles, and fleas, _Monopsyllus eumolpi_ Rothschild.

~Spermophilus tridecemlineatus pallidus~ J. A. Allen, 1874

Thirteen-lined Ground Squirrel

_Specimens examined_ (22).--2 mi. N, 5 mi. W Ludlow, 5; 19 mi. N, 1 mi.

E Camp Crook, 2; 2 mi. S, 2 mi. W Ladner, 1; 6-1/2 mi. N, 2 mi. W Camp Crook, 1; 1/2 mi. W Reva, 3; 4 mi. S, 1/2 mi. W Reva, 1; 6 mi. W Reva, 7; 15 mi. S, 4 mi. W Reva, 1; 7 mi. S, 4-1/2 mi. E Harding, 1.

Ground squirrels are common in areas of short gra.s.s; we observed them most frequently along roadways and fencerows in otherwise overgrazed flats. Many of our specimens were shot or taken in break-back traps baited with rolled oats in just such situations.

Young from the first litters of the year were above ground by late June and represented the largest segment of the population at that time; for example, only three of 17 individuals collected from June 20 to 27 were adults. Adult females collected on June 20 and July 7 had enlarged mammae but were no longer lactating.

Time of emergence from hibernation in northwestern South Dakota is unknown, but many ground squirrels were active in the last week of March, 1963. A male obtained on March 28 had testes that measured 27 and was in full winter pelage, which is easily distinguished from the shorter, darker pelage of summer.

~Cynomys ludovicia.n.u.s ludovicia.n.u.s~ (Ord, 1815)

Black-tailed Prairie Dog

_Specimens examined_ (5).--Sec. 25, R. 3 E, T. 22 N, 2; 1-1/2 mi. W Buffalo, 1; 1/2 mi. W Camp Crook, 3200 ft., 2.

The extensive flatlands of short gra.s.ses on relatively deep soils provide ideal habitat for the black-tailed prairie dog in Harding County. Visher (1914:89) mentioned extensive colonies along "flats" of streams and reported one "town" west of the Little Missouri River that covered several sections and another "on the table of the West Short Pine Hills." Recently, emphasis on control of numbers of prairie dogs in the area has reduced many formerly extensive colonies to small, disjunct units. According to Robert Kriege (personal communication, 1968), a "town" of approximately 3000 acres, about five miles east of the Little Missouri River (in R. 2 E, T. 21 N), is the largest remaining in the county. Thirteen other colonies then known to him ranged in approximate size from 25 to 300 acres.

White-colored prairie dogs apparently are not uncommon in some areas of the county and local residents reported to us a number of instances of sighting such individuals. One "town" located 7-1/2 mi. N and 12 mi. W Ladner, in the northwestern corner of the county, contained at least six families of white individuals, congregated together at the edge of the colony, in the spring of 1968. White prairie dogs also were noted by one of our field parties in 1963 in a "town" formerly located 7-1/2 mi. W Buffalo.

~Tamiasciurus hudsonicus dakotensis~ (J. A. Allen, 1894)

Red Squirrel

Visher (1914:88) reported that he obtained a red squirrel in the Long Pine Hills, along the western border of Harding County, in July of 1910 and noted that the species had been reported to him as occurring also in the West Short Pine Hills. Visher's record evidently has been overlooked by subsequent cataloguers (see, for example, Hall and Kelson, 1959: map 257). Insofar as we can ascertain, _T. hudsonicus_ does not now occur on any of the pine-clad b.u.t.tes and ridges of the county, although the species is present in relatively dense stands of ponderosa pine in the Long Pine Hills of adjacent Carter County, Montana, at a place only a few miles west of the South Dakota border. Probably some individuals stray into the relatively small and spa.r.s.ely-wooded areas of the Long Pine Hills that extend eastward to the north of Camp Crook.

On the basis of color, specimens we have examined from the Long Pines clearly are a.s.signable to _T. h. dakotensis_ rather than to _T. h.

baileyi_, substantiating in part the statement of the distribution of _dakotensis_ published by Miller and Kellogg (1955:263).

~Th.o.m.omys talpoides bullatus~ Bailey, 1914

Northern Pocket Gopher

_Specimens examined_ (22).--NE 1/4 sec. 22, R. 1 E, T. 23 N, 1; 7 mi. N, 2-1/2 mi. W Camp Crook, 3300 ft., 3; Camp Crook, 1; 10 mi. S, 5 mi. W Reva, 10; 10 mi. S, 4 mi. W Reva, 4; 2 mi. S, 5 mi. E Harding, 2; Crow b.u.t.tes, 1 (USNM).

The northern pocket gopher probably occurs in most areas of northwestern South Dakota where the soil is sufficiently deep for constructing burrows, but we found it commonest in the lower gra.s.sy slopes of b.u.t.tes and in relatively sandy areas along some of the major streams.

A female obtained on June 20 contained two embryos that measured 3.

Testes of an adult male trapped on May 18 measured 19 and those of one taken on July 6 measured 9. Juveniles were collected in both May and June.

Bailey (1915:102) referred a specimen from Crow b.u.t.tes to _T. t.

bullatus_, but Swenk (1941:3), in the original description of _T. t.

pierreicolus_, suggested that this same specimen "probably" was referable to the latter because he a.s.sumed it came from soils of the Pierre series. However, Baker (1952:8) included the Crow b.u.t.tes in the h.e.l.l Creek formation and, in any event, one of us (Jones) examined the specimen in question and found it clearly referable to the subspecies _bullatus_. Over and Churchill (1945:32) erroneously a.s.signed pocket gophers from northwestern South Dakota to two different subspecies (_bullatus_ and _clusius_), referring at least one individual from Harding County to _T. t. clusius_.

Fleas, _Dactylopsylla ignota_ (Baker), were found on one individual examined. Molting adults were taken in each month from May through August.

~Perognathus fasciatus fasciatus~ Wied-Neuwied, 1839

Olive-backed Pocket Mouse

_Specimens examined_ (16).--2 mi. N, 5 mi. W Ludlow, 3; 4 mi. S, 7 mi. W Ladner, 9; 10 mi. S, 5 mi. W Reva, 1; 14 mi. S, 4 mi. W Reva, 2; 15 mi.

S, 4 mi. W Reva, 1.

This pocket mouse is not uncommon in areas of short gra.s.s and sage in Harding County. None of five adult females taken late in June was pregnant or lactating, but three had enlarged mammae indicative of reproductive activity earlier in the spring, to which young of various sizes in our series also attest. Active molt was evident on adults taken on June 19, 26, and 28.

Our specimens are intergrades between _Perognathus fasciatus fasciatus_ and the paler _P. f. olivaceogriseus_. Average external measurements of seven adults (two males and five females) are: total length, 138.0 (130-150); length of tail, 65.3 (59-74); length of hind foot, 17.1 (15-18.5); length of ear (six specimens only), 6.8 (6-7); weight in grams (five specimens only), 12.9 (11.2-14.6). Selected cranial measurements of the two males and two of the females are, respectively, as follows: occipitonasal length, 24.0, 23.2, 23.5, 22.3; interorbital breadth, 4.9, 5.2, 5.0, 5.0; mastoid breadth, 13.0, 13.1, 12.2, 11.9; length of maxillary toothrow, 3.3, 3.3, 3.1, 3.4.

~Perognathus hispidus paradoxus~ Merriam, 1889

Hispid Pocket Mouse

An adult female, not reproductively active, that was trapped in rather spa.r.s.ely vegetated rangeland to the southwest of Slim b.u.t.tes (14 mi. S and 4 mi. W Reva) on July 19, 1961, is the only specimen of the hispid pocket mouse on record from Harding County. Other species of small mammals taken in the same or adjacent traplines were _Perognathus fasciatus_, _Dipodomys ordii_, _Reithrodontomys megalotis_, _Peromyscus maniculatus_, and _Onychomys leucogaster_.

A single individual reported from Wade, Grant Co., North Dakota, by Bailey (1927:123), approximately 100 miles to the northeast, is the only specimen known from a more northerly locality.

~Dipodomys ordii terrosus~ Hoffmester, 1942

Ord's Kangaroo Rat

_Specimens examined_ (13).--NE 1/4 sec. 22, R. 1 E, T. 23 N, 6; 2 mi. N, 5 mi. W Ludlow, 1; 2 mi. S, 11 mi. W Reva, 1; 14 mi. S, 4 mi. W Reva, 4; 15 mi. S, 4 mi. W Reva, 1.

Ord's kangaroo rat is found in spa.r.s.ely vegetated flatlands throughout Harding County, although it appears to be uncommon except in localized areas of relatively sandy soils. Five of seven specimens taken from June 18 through 24, 1961, were young of the year, as were three of six individuals trapped on May 31, 1968. One adult female (81.1 grams) obtained on May 31 was lactating and had four placental scars, whereas another that weighed 67.2 grams evidenced no recent reproductive activity. An adult male (67.9 grams) taken on May 31 had testes that measured 9; those of a subadult male (46.5 grams) taken on the same date measured only 6.

The two May-taken adult females mentioned above still were completely in winter pelage, but the adult male trapped at the same time was molting.

An adult male (57.2 grams) obtained on June 22 had completed molt save for a small patch between the ears and immediately behind the head.

~Castor canadensis missouriensis~ Bailey, 1919

Beaver

_Specimens examined_ (2).--Sec. 22, R. 1 E, T. 20 N, 1; 32 mi. SE Buffalo, 1.

According to local residents, the beaver is common along many of the water courses in the county. One of our two specimens came from a tributary of the Little Missouri River north of Camp Crook and the other was taken from a tributary of the Moreau River in the southeastern part of the county. Robert Kriege of Buffalo reported to us that beaver are not restricted to wooded areas, but frequently inhabit streams and more or less permanent impoundments bordered by gra.s.sland. In such places they are said to construct bank dens and eat princ.i.p.ally sage and forbs.

Visher (1914:89) reported this species along the Little Missouri River, Boxelder Creek, the forks of Grand River, Bull Creek, and "Devil's Gulch" in the North Cave Hills, and figured (pl. 6) a dam on Rabbit Creek. We have observed evidence of beaver activity along the Little Missouri River southwest of Ladner and along aspen-wooded stream banks in the Short Pine Hills, where in the spring of 1963 abundant sign was found.