1936] 



MAMMALS OF OREGON 



187 



in long leaps through the air. Their real homes are back in cracks 

 and little caverns of the cliffs, where their tiny tracks show on dusty 

 shelves, and where traps baited with rolled oats get a few speci- 

 mens. They seem never to be numerous and are very local in dis- 

 tribution. They are caught only at night and, like other members 

 of the genus, seem to be closely nocturnal. 



Breeding habits. The females have but 2 pairs of mammae, all 

 close together on 1 pair of mammary glands well back on the abdo- 

 men. The usual number of young is probably 2 or 4 as in other 

 members of the group and the slow rate of reproduction may well 

 account for the rarity of the species. 



Food habits. Little shells and husks of a great variety of seeds 

 scattered along their rocky shelves in well-hidden holes of the rocks 

 show the general nature of their food. Hackberry shells are often 

 found, and chaff from grass seeds and bits of wild currant and 

 rose seeds under the bushes at the foot of cliffs give some clue to 

 their diet. The stomach contents show mainly a white dough from 

 well-masticated seeds with occasional traces of insects. Rolled oats 

 is a favorite bait, but almost any grains or seeds are eaten, also 

 bread, meat, or other of our standard foods. 



Economic status. In their cliffs and canyons these mice fill a 

 niche at present unoccupied by man and only in rare cases can 

 they be considered in any way harmful. 



PEROMYSCUS TRUEI GILBERTI (ALLEN) 

 GILBERT'S WHITE-FOOTED MOUSE 



Sitomys gilberti Allen, Amer. Mus. Nat. Hist. Bull. 5 : 188, 1893. 



Type. Collected in Bear Valley, San Benito County, Calif., by C. H. Gilbert 

 and W. W. Price in 1893. 



General characters. Large ; 

 ears very large and nearly 

 naked ; tail about half of to- 

 tal length, long haired at tip. 

 Skull long and narrow with 

 especially long rostrum ; mam- 

 mae in three pairs. Adults, 

 upper parts dark rich cinna- 

 mon, considerably darkened 

 over back by dusky; top of 

 tail brownish black; feet, 

 lower parts, and lower h,alf of 

 tail whitish. Immature, dark 

 plumbeous over upper parts. 



Measurements. Average of 

 a series of typical adults: 

 Total length, 200 mm ; tail, 

 98; foot, 24; ear (dry), 20. 



FIGURE 38. Range of Gilbert's and Treble's white- 

 footed mice in Oregon : 1, Peromyscus truei ffil- 

 lerti; 2, P. t. preWei. Type locality circled. 



Distribution and habi- 

 tat. From the interior 

 valleys of California 



these big-eared mice extend northward from the Klamath River 

 Valley into the Rogue River Valley, where specimens have been taken 

 at Grants Pass, Grants Peak, Galice, Brownsboro, and Briggs Creek 

 (fig. 38) . They occupy Upper Sonoran Zone, generally in open forest, 

 chaparral, or cliff country. 



