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 grassland. In such places
they are said to construct bank dens and eat principally 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.

~Reithrodontomys megalotis dychei~ J. A. Allen, 1895

Western Harvest Mouse

_Specimens examined_ (27).--NE 1/4 sec. 22, R. 1 E, T. 23 N, 1; 4 mi. S,
7 mi. W Ladner, 3; 2 mi. N, 5 mi. W Ludlow, 7; 1/2 mi. W Reva, 14; 10
mi. S, 5 mi. W Reva, 1; 14 mi. S, 4 mi. W Reva, 1.

The western harvest mouse was taken commonly in stands of tall grasses
and forbs, particularly along roadways and fencerows. Occasional
individuals were trapped in areas of mixed shrubs and grasses. Four
pregnant females taken in late June carried the following number of
embryos (crown-rump lengths in parentheses): seven