SMALLER MAMMALS OF NORTH AMERICA 



427 



plemented by trapping or poisoning in open 

 places. Campaigns of this kind can be fully 

 successful only when engaged in 'by the com- 

 munity at large. The returns from the invest- 

 ment for such a purpose will be large, not 

 only in the vast money values of property 

 saved, but in the reduction of the death rate and 

 in the great improvement of the public health. 



THE HOUSE MOUSE (Mus musculus) 



(For illustration, see page 429) 



The familiar house mouse is of Old World 

 origin and may be distinguished from most of 

 our native mice by its proportionately slen- 

 derer body, long hairless tail, and the nearly 

 uniform color on the upper and under parts 

 of the body. Like the house rat, wandering 

 an alien from its original home in Asia, and 

 transported by ship and by inland commerce, 

 it has gained permanent foothold and thrives 

 in lands of the most diverse climatic condi- 

 tions, except those of the frigid polar regions. 



For centuries the house mouse has been par- 

 asitic about the habitations of man, and in 

 many places in America has spread into the 

 surrounding country, where it holds its own in 

 the struggle for existence with many of our 

 native species. It is probable that its ability 

 to live in houses also infested by the fierce 

 brown rat is due wholly to its agility, and to 

 the small size, which enables it to retreat 

 through crevices too small for the rat. 



In buildings it hides its warm nests in ob- 

 scure nooks and crannies, making them of 

 scraps of wool, cotton, or other soft fibrous 

 material, often cut from fabrics. Out in the 

 fields, like any other hardy vagabond, it adapts 

 itself to whatever cover may be available on 

 the surface or in crevices and the deserted 

 burrows of other mammals. 



It has several litters of from four to nine 

 young each year. The young are born blind, 

 naked, and helpless, but are soon able to run 

 about, often following the mother on her for- 

 aging expeditions. When a little more than 

 half grown they usually scatter from the home 

 nest and seek locations of their own. 



Throughout most of its world-wide range 

 the house mouse has the same general appear- 

 ance, but in some localities the effect of 

 changed environment is developing appreciable 

 differences, which appear destined to result in 

 marked geographic races. The representatives 

 of these mice I caught in weedy fields on the 

 coast of Chiapas, near the border of Guate- 

 mala, have an appreciable rusty shade on the 

 back in place of the ordinary dull gray. 



The success of both the house mouse and 

 the house rat in establishing themselves so suc- 

 cessfully in all parts of the world, in the face 

 of the antagonism of mankind, affords marvel- 

 ous examples of physical and mental adapta- 

 bility not equaled elsewhere among mammals. 



From early days the domestic mouse has 

 been a familiar member of the household with 

 people of all degree, and the housewife has had 

 to match her wits against the cunning persist- 



ence of this small marauder in order to safe- 

 guard the family supplies of food and clothing. 



Despite the antagonism excited by its de- 

 structive habits the mouse is so small and often 

 so amusing in its ways that it has commonly 

 been regarded with a half hostile, half friendly, 

 interest. This is apparent by frequent refer- 

 ences to it in proverbs, nursery rhymes, fables, 

 and folklore, as well as in more serious litera- 

 ture. 



Many cases of singing house mice have been 

 recorded, their notes being a series of continu- 

 ous musical chirps, trills, and warblings, rising 

 and falling about an octave and slightly resem- 

 bling the song of a canary. It has been claimed 

 that this singing is due to an affection of the 

 songster's breathing organs, but this can 

 scarcely account for its being uttered at definite 

 times and places and ceasing at the volition of 

 the performer. 



In one instance the song had been heard in a 

 china closet and an observer sat by the open 

 door to locate the singer. After patient wait- 

 ing ''a mouse peered out from behind the 

 plates, climbed up a little way on the brackets, 

 and after looking around several times, began 

 to sing." This mouse continued to sing in the 

 same place at intervals for several weeks and 

 became accustomed to the presence of people 

 during its performances; then it suddenly dis- 

 appeared, probably a victim to one of the dan- 

 gers which constantly beset its kind. 



THE MOUNTAIN-BEAVER (Aplodontia 

 rufa phaea and its relatives) 



(For illustration, see page 432) 



The first adventurous fur traders who pene- 

 trated the Oregon wilds found the Chinook 

 Indians provided with robes made of skins of 

 the mountain-beaver. From that time until re- 

 cently but little accurate information has been 

 available concerning the habits of this curi- 

 ous animal. Locally it is known by several 

 other names, including "Sewellel," "mountain 

 boomer," "boomer," and, in the Olympic moun- 

 tains, "chehalis." 



The genus of mountain-beavers contains only 

 a single species with several subspecies, all hav- 

 ing a close superficial likeness in size and form 

 to a tailless muskrat, except for their coarse, 

 harsh fur. It is an exclusively North Amer- 

 ican type and, aside from a remote relationship 

 to the squirrel family, has no kin among liv- 

 ing mammals. It appears to be a sole survivor 

 from some former age. As with the pocket 

 gophers, its mode of life has developed power- 

 ful muscles about the head, front legs, and 

 forepart of the body. 



The distribution of the mountain-beaver in 

 Tertiary times extended through the Great 

 Basin to North Dakota, but at present is 

 closely restricted to the humid region between 

 the crests of the Cascades and the Sierra 

 Nevada and the Pacific coast, and from the 

 lower Fraser River, British Columbia, south to 

 the latitude of San Francisco Bay. California. 



Within this superbly forested region this ani- 



