356 



NORTH AMERICAN FAUNA 



[No. 55 



Distribution and habitat. Mountains of Oregon as well as the 

 whole Cascade and Sierra Nevada and Rocky Mountain systems of 

 North America from Alaska to central Arizona, generally in 

 Canadian Zone, or along streams of cold water just below the zone 

 (fig. 84). 



General habits. These beautiful large long-tailed shrews are more 

 than any other of our North American species adapted to aquatic 

 life and are almost invariably found along the margins of small 

 streams, springs, or ponds. They live in holes in banks, under logs, 

 or under any cover where it is moist and cool and convenient to the 

 water, from which their food is largely obtained. With the large 

 bristle-margined feet and toes they can fairly run over the top of the 

 water or dive and swim with great speed and skill, while their 

 velvety fur is as waterproof as the feathers of a diving duck. At the 

 edge of a little clear cold mountain lake near the north base of the 



Three Sisters Peaks one of 

 these little animals was 

 seen as it ran under an old 

 log near the water. The 

 log was rolled over and 

 the shrew was caught in 

 the hands, to which act it 

 showed vigorous and fu- 



FIGURB 84. Range of the water shrew, Nepsorex 

 lustris navigator, in Oregon. 



tile objection by trying to 

 bite. Tofacilitatefurther 

 observations a thread was 

 looped around one leg and 

 the shrew was let go in the 

 edge of the lake. At first 

 it puffed its fur and sat 

 on top of the water like a 

 duck while it tried to bite 

 the thread from its leg. Soon abandoning this endeavor, it swam 

 along the surface to a log and climbed on it, shook itself dry, ran 

 along a little way and dived into the water again, darting about un- 

 der and over submerged logs and sticks as rapidly and gracefully as 

 a fish. In fact, from its motions and the shining layer of air which 

 clung to the surface of the fur it strongly resembled a silvery fish. 

 The otter had always seemed the most graceful and skillful aquatic 

 mammal, but this tiny creature surpassed any 4-f ooted creature of the 

 writer's acquaintance in its relative speed and skill in the water. 



The fact that these shrews are not often seen except when col- 

 lected for specimens in traps set along the water's edge is due in 

 part to their being largely nocturnal in habits and partly to the 

 observer's failure to recognize them in the water. They are not 

 uncommon in suitable country as shown by good series of specimens 

 from numerous localities over the State. 



Breeding habits. Data on this subject are meager. One female 

 collected at the north base of Three Sisters Peaks on July IT, 

 1914, contained T very small embryos. There are other records of 

 5 and 6 embryos at varying seasons during the summer. The regular 

 number of mammae is 6, 2 pairs of inguinal and 1 pair of abdominal. 



