Comparative Ecology of Pinyon Mice and Deer Mice in Mesa Verde National Park, Colorado

by Charles L. Douglas

Fig. 13: Photograph of microclimatic station at the Pinyon-Juniper-Muttongrass Site, at trapping station D5b of the grid south of Far View Ruins. Grass in the foreground is muttongrass, Poa fendleriana.

The instruments used in this study were unmodified Belfort hygrothermographs containing as sensing units a hair element for relative humidity and a Bourdon tube for air temperatures. The hair element, especially, does not register changes in humidity at precisely ground level; rather, it reflects changes in the layer of air from about ground level to about a foot above. Thus data from these instruments give only approximations of the conditions under which mice live while they are on the ground.

Climatic conditions greatly influence trapping success. Larger numbers of mice generally were caught on nights when humidities were higher than average. Rain in part of the evening almost invariably resulted in more mice of each species being caught. This was probably due to increased metabolism, by the mice, to keep warm. Apparently the mice began foraging as soon as the rains subsided; mice were always dry when caught after a rain. Few mice were caught if rains continued throughout the night and into the daylight hours.

Table 4—Monthly Averages of Daily Means for Maximum, Minimum, and Mean Air Temperatures and Relative Humidities at Four Sites in Mesa Verde National Park, Colorado.

Site	Maximum Temps.					Maximum R. H.
	J	J	A	S	O	J	J	A	S	O
Far View Sagebrush	89	91	86	77	74	68	84	82	88	71
Drainage	86	91	85	78	78	87	94	93	96	84
Oak Brush	86	88	82	76	81	57	78	80	80	66
Pinyon-Juniper-Poa	75	80	74	66	64	59	83	82	88	58
	Minimum Temps.					Minimum R. H.
	J	J	A	S	O	J	J	A	S	O
Far View Sagebrush	42	53	50	42	31	18	24	25	29	21
Drainage	36	48	45	38	26	21	26	27	29	30
Oak Brush	42	52	50	42	32	19	25	30	31	21
Pinyon-Juniper-Poa	44	54	50	42	34	22	30	29	32	25
	Mean Temps.					Mean R. H.
	J	J	A	S	O	J	J	A	S	O
Far View Sagebrush	66	72	68	60	52	43	54	54	48	46
Drainage	61	70	65	58	52	54	60	60	62	52
Oak Brush	64	70	66	59	56	38	51	55	56	44
Pinyon-Juniper-Poa	60	67	62	54	49	41	56	55	60	42