SHREWS 49 



The shrews, though of small bodily size as individuals, constitute, by 

 reason of their numbers and their great activity, an important biological 

 group in the fauna of the Yosemite region. They are actually "micro- 

 carnivores" and exhibit an even greater degree of voracity than do the 

 larger and better known flesh-eating species such as weasels, martens, and 

 wildcats. Shrews kept in captivity have been known to eat more than 

 their own weight of flesh in twenty-four hours. If they do this while in 

 confinement there is no reason to suppose that their capacity would be 

 any less (but rather more) when they are traveling about with full freedom 

 in the wild. It is a common experience among naturalists who are trapping 

 to find each morning one or more of the specimens in the traps mutilated 

 to a greater or less degree. Numerous cases of this kind came to notice 

 while we were engaged in field work in the Yosemite region. A part at 

 least of this work may fairly be attributed to shrews, though various species 

 of small rodents are known to eat maimed, trapped, or dead individuals 

 of their own kind. Where only a beginning on the feast has been made, 

 it is usually the brain of the trapped animal that is eaten. But not infre- 

 quently the work is done so completely that only a few fragments remain — 

 scarcely enough to identify the victim. Not only rodents but even trapped 

 shrews sufi'er from attacks of this sort. And this cannibalistic tendency 

 has been reported by observers who have kept shews in captivity. When 

 any of the large carnivorous mammals, such as a coyote or a fox, raids a 

 trapped specimen, the trap and all frequently disappear; if carnivorous 

 beetles go after such prey, they accomplish but little in a single night; 

 but if the shrews find the victim, they are apt to make short work of it, 

 and without disturbing the trap in any way. 



Evidence of several kinds shows that shrews forage to some extent by 

 day as well as during the hours of darkness. It is likely that they depend 

 less upon sight in searching for prey than upon the senses of smell, touch, 

 and hearing. 



As an indication of the density of population among the small mammals 

 in a favorable location, and also of the extent to which shrews (in this 

 case the Dusky Shrew) 'police' the ground in search of food, a record of 

 trapping near Porcupine Flat may be cited. A line of traps set in a small 

 meadow there from June 27 to July 3, 1915, produced the following 

 mammals: Meadow Mouse, 3; Allen Jumping Mouse, 3; Sierra Nevada 

 Pocket Gopher, 4; Dusky Shrew, 6; total, 16, in six nights of trapping. 

 And the traps were still catching specimens when the line was taken up. 

 This particular meadow had a total area of about 7350 square feet — the 

 size of a large city lot (50x147). The vegetation consisted of grasses, 

 lupines, and a species of orchid. It is possible that so large a number of 

 shrews did not live and forage exclusively within so limited a tract. Only 



