Part 4

Least Chipmunk

Specimens examined (31).--2 mi. N, 5 mi. W Ludlow, 15; NW 1/4 sec. 15, R. 5 E, T. 22 N, 2; 2 mi. S, 3-1/4 mi. W Ludlow, 2; NW 1/4 sec. 32, R. 1 E, T. 20 N, 1; 9 mi. S, 7 mi. W Reva, 1; 10 mi. S, 5 mi. W Reva, 9; NE 1/4 sec. 8, R. 8 E, T. 16 N, 1.

The least chipmunk is common in the buttes and associated badlands where it most frequently inhabits rocky areas. Visher (1914:88) reported E. minimus from Harding County ("abundant in badlands"), but his paper has been overlooked by most subsequent workers. Visher's mention of a chipmunk from the mouth of the Moreau River in north-central South Dakota, incidentally, would seem to be in error, as would the report by Over and Churchill (1945:28) of Eutamias inhabiting "... thickets along the Little Missouri River of Harding County."

Females evidently bear but one litter annually (in late May) in northwestern South Dakota and young are weaned by the latter part of June. Females taken on May 15 and 19 carried embryos (five measuring 30 and three measuring 28, respectively). A lactating female with five placental scars was obtained on May 24, but eight adult females taken after June 23 previously had weaned young. Juveniles were collected on June 24 and 25. Testes of two adult males collected in mid-May measured 11 and 18, but males taken in summer had much smaller testes.

In late spring, most adult least chipmunks molt from the worn, drab-gray pelage of winter to a brighter, more tawny summer pelage, but molt in a few females, perhaps originally delayed by reproductive activity, continues well into the summer months. Of seven specimens taken between May 15 and 24, two (one male and one lactating female) were in an early stage of molt, whereas the remainder were in winter pelage. Nine specimens (four females and five males) taken in mid- and late June were molting, but two females collected then were in winter pelage, and three animals, two males and a female, had completed molt to summer pelage. One adult female taken on August 5 had yet to complete molt to summer pelage. In our material, the first indication of molt from winter to summer pelage appears on the top of the head and the cheeks. Thereafter, molt proceeds posteriorly over the shoulder region and more or less evenly along the back and sides. In two specimens, small patches of molt preceded the general molt line. Molt on the venter apparently begins after molt on the dorsum approaches completion, but we could discern no definite pattern; on four specimens, hair was being replaced on the venter in scattered patches.

An August-taken young of the year engaged in post-juvenal molt had new adult pelage in a vague hour-glass pattern in the dorsal trunk region as well as on the cheeks and anterior part of the head. It was actively molting on top of the head, between the ears, over the shoulders, laterally behind the front feet, and along the sides, and had old pelage on the rump. Ventrally, the new adult pelage was evident only along the midline.

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 grass; 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 ludovicianus ludovicianus~ (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 grasses 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 buttes 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 sparsely-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 assignable 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).

~Thomomys 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 Buttes, 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 grassy slopes of buttes 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 Buttes 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 assumed it came from soils of the Pierre series. However, Baker (1952:8) included the Crow Buttes in the Hell 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 assigned 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.