188 



NORTH AMERICAN FAUNA. 



[NO. 27. 



Fort Anderson ; and Fort McPherson, have been referred to M. drum- 

 rnond'K and recorded by Bailey.'^ 



During the autumn of 1900 great numbers of mice, probably mainly 

 of this species, overran central SaskatcheAvan and central Alberta. 

 The}^ entered the storehouses and committed great havoc wherever 

 grain or other food was stored. Immense numbers, many of which 

 were floating down the rivers, were found dead. Throughout the 

 country between Edmonton and Athabaska Landing we found abun- 

 dant evidence of their former presence, but fresh runways were only 

 sparingly noted, showing that most of the animals had disap- 

 peared. This invasion must have extended over a very large extent 

 of country. I was informed by W. A. Burman, of Winnipeg, that 

 small rodents were so common in Manitoba during the same autumn 

 that ftir-bearing animals were trapped with much difficulty, their 

 natural food being so easily obtained. 



Microtus (Microtus) xanthognathus (Leach). Chestnut-cheeked Vole. 



This large vole occurs locally nearly throughout the wooded region. 

 Although it inhabits the valley of the Athabaska, we did not detect it 

 in the summer of 1901 until we reached Fort Smith, where we found 

 a colony and secured a series of about 20 adults. This colony in- 

 habited a strip of young mixed woods bordering a marsh about half 

 a mile south of the post. The burrows of the animals were in dry 

 ground in the woods or shubbery, and evidently were quite deep, as 

 I saw nearly a bushel of dirt at the entrance of a single burrow. From 

 the burroAvs their well-trodden runways extended in various direc- 

 tions to a distance of 50 or 75 yards, only rarely reaching wet or even 

 damp ground. As a rule only a pair was taken in one set of run- 

 ways. The favorite food seemed to be the stems of Equisetum,^ which 

 grew luxuriantW in their haunts. Only old ones were secured, the 

 young evidently not being large enough to run about, though several 

 of the females had recently borne litters. A female taken June 19 

 contained 11 well-developed embryos. The measurements of 10 

 adult specimens from this locality average: Total length 212.6, tail 

 vertebra^ 52.8, hind foot 24.5. At Fort Kesolution my brother took 

 a few specimens during July, but was unable to find any colony. At 

 Trout Rock, 25 miles south of Fort Rae, I found a small community, 

 and took 3 adults and a number of quarter-grown young on July IT 

 and 18. Contrary to their usual habit, the individuals of this colony 

 had extended their runways into a wet sphagnum swamp. At Fort 

 Rae I was unable to find any evidence af the presence of this mouse, 

 though the Indians informed me that the species inhabited the 

 vicinity. 



^ N. A. Fauna, No. 17, p. 23, 1900. 



