144 ANIMAL LIFE IN THE YO SEMITE 



Pocket Mice. Genus Perognathus Maximilian^ ^ 



Field characters. — Size small, body size usually about that of House Mouse; tail 

 long, about equal to head and body (pi. 26b, c) ; forelegs and feet short and small; 

 hind feet long and relatively large (see footnote for detailed measurements) ; a fur- 

 lined pouch in each cheek, opening at side of mouth. Coloration yellowish brown above, 

 white on under surface. Workings: Small holes about % to l^/l inches in diameter, 

 usually in sandy soil about bases of bushes; occupied holes plugged with earth during 

 daytime. 



Occtirrence.- — Eesident at lower altitudes on both sides of Sierra Nevada, from 

 Snelling east to El Portal and again around Mono Lake, east of the mountains. i- Lives 

 chiefly in areas of sand or other easily worked soil. Nocturnal. 



The pocket mice constitute but one of several groups of small nocturn- 

 ally active animals which pass unnoticed, even in places where they are 

 abundant, unless special search is made for them. The naturalist when 

 hunting for pocket mice looks at the loose sandy or fine soil about the bases 

 of desert, valley, or foothill bushes, and if he finds little burrows plugged 

 with earth he sets his traps there with the expectation of capturing some of 

 the animals when they come abroad at night. They may not, however, 

 take the bait (usually rolled oats or cornmeal is used) and will thus 

 refuse to disclose their specific identity. The pocket mice are diminutive 

 relatives of the kangaroo rats, their mode of life and niche or place in 

 nature being much the same. 



12 Three distinct species of Pocket Mice occur in the Yosemite region; in fact two 

 distinct systematic groups are represented. But they are all treated together here, due 

 in part to our scanty knowledge of their habits and in part to the slight attention that 

 is likely to be given to such elusive animals by most visitors to the region. It will be 

 noted that the ranges of these three species do not overlap, so that specimens found in 

 the field can be referred with confidence to the proper species on the basis of locality 

 alone. 



California Pocket Mouse, Perognathus californicus californicns Merriam, a large- 

 sized spiny-haired species (pi. 26?;) which occurs widely through the Upper Sonoran Zone 

 in central California, was found from Pleasant Valley eastward to Smith Creek (6 miles 

 east of Coulterville) and to El Portal where it lives on dry chaparral-covered slopes. The 

 largest and darkest colored species in the region. Head and body 3i/-, to 3i/4 inches 

 (81-90 mm.), tail 4 to 5 inches (103-125 mm.), hind foot about 1 inch (24-27 mm.), 

 ear from crown % to ^/^ inch (8-14 mm.), weight % to 1 ounce (19.9-30.0 grams). 

 Pelage coarse with many long grooved spine-like over-hairs on side and rump ; tail with 

 a 'pencil' or tuft at tip; soles of hind feet naked. Upper surface reddish buff, darkened 

 by numerous black hair tippings; under surface white. 



San Joaquin Pocket Mouse, Perognathus inornatus inomatus Merriam, a small- 

 sized, soft haired species (pi. 26c) of the San Joaquin Valley, was recorded at Snelling 

 where it lives in sparse grass on the dry mesa. Head and body 2% to 2% inches (65-74 

 mm.), tail 21/2 to 3% inches (66-79 mm.), hind foot % to % inch (17-20 mm.), ear 

 from crown % inch (8-9 mm.), weight about ^/^ ounce (10.2 grams). Tail not tufted. 

 Coloration pale sandy bufp above, with numerous black hair endings; under surface 

 pure white. 



Great Basin Pocket Mouse, Perognathus parvus olivaceus Merriam, a medium- 

 sized, soft haired species distributed through much of the Great Basin count ry east 01 

 the Sierra Nevada, was found abundantly in the neighborhood of Mono Lake, being 

 recorded from Silver Lake and near Walker Lake north and east to Mono Lake Post 

 Ofiice and Mono Mills. It inhabits dry sandy situations and makes its burrows under 

 sagebrush. Head and body 2% to 3% inches (69-92 mm.), tail 3% to 4 inches 

 (80-100 mm.), hind foot % to 1 inch (22-26 mm.), ear from crown about i/i inch 

 (6-7 mm.), weight % to % ounce (12.5-25.3 grams). Tail not tufted. Coloration 

 above plain buff, with many black hair endings; under surface pure Avhite. 



