1936] MAMMALS OF OREGON 213 



left open in places where the mice come out to feed or where a hard 

 trail cuts across their line of progress, but so well hidden are the runs 

 that few specimens are taken by inexperienced collectors, even where 

 the animals are fairly common. They are easily caught, however, 

 by digging down and setting the trap across the burrow a little 

 below the bottom level. 



Breeding habits. The females have normally 4 pairs of mam- 

 mae 2 inguinal and 2 pectoral 2 on each of 4 distinct mammary 

 glands. The young as shown by embryos usually number 3 to 5, and 

 the records indicate May to August as the main breeding season. 

 This season may be only apparent, however, as comparatively few 

 specimens have been taken in winter, and the breeding season may 

 be more or less continuous throughout the year. 



Food habits. Comparatively little is known of the food habits 

 of these mice beyond what is gathered from the few bits of green 

 grass and other little plants found scattered about their burrows or 

 along the lines of their surface trails. The abundance of camas and 

 other underground bulbs and roots in their territory would suggest 

 a diet mainly from subterranean sources, varied in times of scarcity 

 by any green vegetation available. At times they will take rolled 

 oats as trap bait but again refuse to touch them, and the traps must 

 be set so they will be sprung without regard to bait. 



Economic status. There are few complaints of damage by these 

 little burrowers, but they will bear watching and merit a much closer 

 study of habits than has thus far been made. Injury to root crops, 

 shrubbery, vines, and trees attributed to other rodents may be due in 

 part to them. 



MICROTUS OREGONI BAIRDI MERBIAM 

 BAIRD'S CREEPING MOUSE 



Microtus bairdi Merriam, Biol. Soc. Wash. Proc. 11 : 74, 1897. 



Type. Collected on Glacier Peak, northwest side of Crater Lake, Oreg., at 

 7,800 feet altitude, by Merriam and Bailey, in 1896. 



General characters. Similar to oregorii but colors lighter, brighter, and 

 mainly clear yellowish bister above ; lower parts lightly washed with whitish ; 

 feet and nose dusky ; tail slightly bicolor, dusky above, dark gray below. 



Measurements. Type specimen, adult female : Total length, 131 mm ; tail, 33 ; 

 foot, 17.5; ear (dry), 9. 



Distribution and habitat. As yet no typical specimens of this 

 form have been taken beyond the "type locality on an open timber- 

 line ridge northwest of Crater Lake, where in the open exposed 

 Hudsonian Zone they were living under beds of heather (fig. 48). 

 Undoubtedly they have a more extended range along the higher levels 

 of the Cascades, where the light and exposure have modified them 

 into a recognizable form. 



Nothing is known of their habits except from the two specimens 

 trapped in the beds of short grass, sedges, and heather close to exten- 

 sive snow banks that were lying late in August on the wind-swept 

 north slopes of Glacier Peak. 



