220 Field Museum of Natural History — Zoology, Vol, XI. 



Prairie Meadow Mouse or Prairie Vole {Microtus ochrogaster). 



opening on one side. This burrow and nest are occupied in winter, 

 and in it at least the first Utter of young is produced in the spring; but, 

 in the summer and fall, these meadow-mice may be found in similar, 

 nests in the grass above ground, in which the young are often, if not 

 usually, brought forth. Nests formed under the snow in winter are 

 also occupied by them. From the burrows, innumerable runways 

 traverse the neighborhood, intersecting those from other burrows, thus 

 forming a complete net-work so that often scarcely a square yard can 

 be found in an acre not crossed by one or more of these tracks. The 

 runways of one pair may sometimes be traced five or ten rods on every 

 side. These roads are not only formed for use in winter, when the 

 ground is covered with snow, but are also employed as highways in 

 summer. They are made above ground by pressing down and gnawing 

 off the grass, and the earth is often worn quite smooth and bare in those 

 most used. The inhabitants can travel easily along them at all times, 

 in search of food, being well concealed by the overarching grass. In 

 winter, these paths are formed on the ground, under the snow, as well 

 as in the grass. The mice do not inhabit prairie pastures, where the 

 grass is eaten close and affords them no cover. 



"Upon examining, in November, the burrow of a pair of these 

 meadow-mice, situated on the wild prairie, I found the excavation to 

 have been recently enlarged. The nest was placed near the centre of 



