ions may exist in Slim Buttes and perhaps elsewhere in the
county. _Zapus hudsonius_ and _Microtus pennsylvanicus_ were trapped in
Deer Draw in association with white-footed mice.

Females collected on June 15 and August 7 were lactating and one taken
on June 20 contained six embryos that measured 15. Two males taken on
June 2 had testes that measured 12 and 15. These two males and a
lactating female taken on June 15 still were in winter pelage, whereas a
non-breeding female obtained on June 15 and a male and female (pregnant)
trapped on June 20 were in summer pelage or an advanced stage of molt to
that pelage. A lactating female taken on August 7 was in summer pelage
excepting that what definitely appeared to be new winter pelage was
present on the head, cheeks, and below the ears, and molt was evident
adjacent to these areas.

Selected average (and extreme) measurements of the seven adults from
Deer Draw are: total length, 184.4 (175-199); length of tail, 77.4
(70-88); length of hind foot, 21.1 (20-22); length of ear, 16.7 (16-18);
greatest length of skull, 27.8 (27.0-28.4); zygomatic breadth, 14.6
(14.0-14.9); least interorbital width, 4.1 (4.0-4.3); length of
maxillary toothrow, 4.2 (4.0-4.4). Three males and two non-pregnant
females weighed 34.9, 34.6, 30.5, 32.2, and 31.4 grams, respectively.

~Peromyscus maniculatus nebrascensis~ (Coues, 1877)

Deer Mouse

_Specimens examined_ (214).--19 mi. N, 1 mi. E Camp Crook, 5; 18 mi. N
Camp Crook, 2; 2 mi. N, 5 mi. W Ludlow, 58; 4 mi. S, 7 mi. W Ladner, 14;
9 mi. N, 3 mi. W Camp Crook, 3400 ft., 3; 7 mi. N, 2-1/2 mi. W Camp
Crook, 3300 ft., 2; NW 1/4 sec. 32, R. 1 E, T. 20 N, 4; 1/2 mi. W Reva,
2; SW 1/4 sec. 30, R. 7 E, T. 18 N, 5; 9 mi. S, 7 mi. W Reva, 3; 10 mi.
S, 5 mi. W Reva, 64; 14-15 mi. S, 4 mi. W Reva, 33; 2 mi. S, 5 mi. E
Harding, 16; 7 mi. S, 4-1/2 mi. E Harding, 3.

The deer mouse is the most abundant and widespread small mammal in
northwestern South Dakota. We took specimens in all terrestrial
habitats, although the species was commonest in upland situations such
as grassy fencerows, rocky areas, and hillsides supporting shrubs,
juniper, or pine.

Adult mice in reproductive condition were taken in each month from May
through August, although most of our information is for the months of
May and June. In the last half of May, seven pregnant females carried an
average of 5.0 (4-6) embryos that ranged in crown-rump length from 2 to
10; three others take