Specimens examined.—Total, 38: North end Mesa Verde National Park, 7000 ft, 75984–75986; Park Point, 8525 ft., 69316–69317; Far View Ruins, 7700 ft, 69318–69319, 79220, MV 7897/507, and 23 uncatalogued specimens in preservative; 3 mi. N Rock Springs, 8200 ft., 69320–69321; 2 mi. NNW Rock Springs, 7900 ft., 69322–69323; 1 mi. NNW Rock Springs, 7600 ft., 69324; ½ mi. NNW Rock Springs, 7500 ft., 69325.
The specimen listed last (69325) was an adult male recovered from the stomach of a small (snout-vent length 334 mm., wt. 26.0 gms.) Crotalus viridus that was trapped in a Museum Special mouse-trap on a rocky slope mostly barren of vegetation. The availability of samples taken in August (by Anderson in 1956), in September (by Shepherd in 1958), and in November (by Alcorn in 1957) makes the following comparison of age and reproductive condition possible. The sample from November includes some specimens from outside the Park as follows: 1 mi. W Mancos, Colorado, 75979–75983, and 2 mi. N La Plata [not shown on [Fig. 2]], San Juan County, New Mexico, some 18 miles southeast of the Park, 75987–76000. The data shown in [Figure 3] indicate that females are pregnant at least from in August into November. A smaller percentage of females was pregnant in November than in August or September. The fact that all females more than 130 mm. long were pregnant in September suggests an autumnal peak in breeding activity. A change in the ratio of small individuals (less than 130 mm. in length) to large individuals (130 mm. or more in length) is indicative of a sustained breeding period throughout the time shown. In August the ratio was 1 to 2.3, in September the ratio was 1 to 1.2, and the ratio was 1 to 0.7 in November. The western harvest mouse is found usually in grassy areas.
Peromyscus boylii rowleyi (J.A. Allen)
Brush Mouse
Specimens examined.—Total, 14: North end Mesa Verde National Park, 7000 ft., 76002–76003; Far View House, 7700 ft., MV 7851/507, 7854/507; Far View Point, 5 uncatalogued specimens in preservative; ½ mi. N Spruce Tree Lodge, 34742; 25 mi. [by road] SW Mancos, 149094 and 149096 USNM; Oak Tree Ruin, 6700 ft., MV 7870/507; and Cliff Palace, 6800 ft., MV 7864/507.
The specimens were taken in August, September, and November. One adult female trapped on September 10, 1958, had six embryos.
Peromyscus crinitus auripectus (J.A. Allen)
Canyon Mouse
Specimens examined.—Total, 3: Mesa Verde [Spruce Tree Cliff Ruins], 149095 USNM; Balcony House, MV 7865/507, 7866/507.
Peromyscus maniculatus rufinus (Merriam)
Deer Mouse
Specimens examined.—Total, 396: North end Mesa Verde National Park, 7000 ft., 76004–76100; Prater Canyon, 7600 ft., 76101–76144, MV 7839/507, 7840/507; Upper Well, Prater Canyon, 7575 ft., 69328–69329; Morfield Canyon, 7600 ft., 76145–76184; Park Point, 8525 ft., 69330–69342, 69344–69360; 1½ mi. E Waters Cabin, 6400 ft. (labels on some specimens read "West Bank Mancos River, Northeast side Mesa Verde National Park"), 69361–69376, 76185–76204; Sect. 27, head of east fork Navajo Canyon, 7900 ft., 69377–69380, 69422–69426; 3 mi. N Rock Springs, 8200 ft., 69403–69410; 2 mi. NNW Rock Springs, 7900 ft., 69411–69412; 1 mi. NNW Rock Springs, 7600 ft., 69413–69418; ½ mi. NNW Rock Springs, 7500 ft., 69419–69421; Far View Ruins, 7700 ft., 69386–69402; Far View Point, 76530–76531, 79221 and 90 uncatalogued specimens in preservative; Mancos River, 6200 ft., 69382–69385; back of Park Museum, 6930 ft., MV 7857/507; Mesa Verde, 25 mi. [by road] SW Mancos, 149093 USNM; Cornfield, MV 7878/507.
The most abundant mammal is the ubiquitous deer mouse. Series of specimens taken in August (by Anderson in 1956), in September (by Shepherd in 1958 and 1959), and in November (by Alcorn in 1957) make possible the following comparisons of age, reproductive conditions, and molts.