102 



NORTH AMERICANi FAUNA 66 



Figure 37. — Distribution of Clethrionomys ffapperi gapperi. 



Measurements. — Ten adults from Garrett County have the follow- 

 ing external and cranial measurements : Total length 147.3 (140-155) ; 

 tail 42.9 (38-48) ; hind foot 19.5 (19-20) ; condylobasal length of skull 

 24.9 (24.1-25.8) ; zygomatic breadth 13.3 (13.0-13.7) ; interorbital 

 breadth 4.0 (3.9-4.2) ; length of molar toothrow 54 (5.2-5.6) . 



Habitat and habits, — ^This mouse prefers cool, damp, forested areas 

 where it lives among the mossy rocks and rotten logs. In the northern 

 part of its range it is widely distributed, but in Maryland it is re- 

 stricted to the higher mountains, where it is locally abundant. Preble 

 (field notes) took the red-backed mouse at Finzel on the border of a 

 hemlock woods, and at Grantsville he found that it was very common 

 in a tract of hemlocks 3 miles east of the town. It was also abundant 

 in the mixed forest covering the steep slopes on the east side of the 

 Castleman Eiver, and in the hemlock woods near Bittinger. At Moun- 

 tain Lake Park, Preble took a specimen among rocks in an oak woods, 

 and at Swanton he trapped a very dark individual in deep hemlock 

 woods. Bookhout tells me that he trapped one in Allegany County in 

 a rock outcrop in a second-growth oak-hickory forest. 



This species does not make elaborate tunnels, but will occupy those 

 made by moles and shrews. Jackson (1961, pp. 227-228) has described 

 a nest in detail. It was located among the rootlets of small trees and 

 was some 3 inches in diameter. The nest was merely a small carpet of 

 grass stems and a few particles of dead leaves and moss, the entire 



