102 ANIMAL LIFE IN THE YOSEMITE 



there being only a very few short hairs and no 'pencil' or tuft at the end. 

 The general coloration is the same over the entire upper surface of the 

 body, a mixed yellowish brown or grayish brown 'ticked' with black hair 

 endings. The under surface of the House Mouse is ordinarily but little 

 paler than the back; many individuals here in California, however, and 

 especially in the Yosemite region are buff or even white beneath ; the latter 

 color, when present, is never so pure as on the White-footed Mouse, and is 

 not so sharply demarked along the sides. The feet are usually dusky- 

 colored, sometimes pale, but never white. The eye of the House Mouse is 

 small, about half the size of the eye of the Common White-footed Mouse. 



A striking similarity in external appearance is found between the House 

 Mouse and the Harvest Mouse, the measurements, proportions of body and 

 tail, and even the coat color being much alike, particularly with light- 

 bellied specimens of Mus. The appearance of the upper incisor teeth at 

 once separates the two, however. In the Harvest Mouse each of these 

 teeth is marked by a vertical groove ; in the House Mouse, the surface of 

 the tooth is perfectly smooth. 



The House Mouse is now well established in the Yosemite region and 

 doubtless has been for a great many years. It was probably quite an early 

 arrival, as the foothill districts bordering the Yosemite were among the 

 first areas settled by white people in California ; and this mouse, in America, 

 has closely followed the white settler. Living about houses and barns, it 

 often makes its nest amid household effects, or in bags of grain or bales 

 of hay. When these are carried to a new locality the mice often go also, 

 as stowaways ; their spread in this manner is thus passive so far as the 

 mice themselves are concerned. When the goods or other articles are set 

 down in a new location the mice, being in new territory, speedily increase 

 and take possession of their surroundings ; and, sooner or later, because 

 of their more aggressive nature, they compel the native small rodents of 

 the neighborhood to give way and finally altogether displace them. 



But the House Mouse at the lower and middle altitudes is not only 

 about man's habitations. At Snelling and as far into the foothills as El 

 Portal this mouse was found living apart from buildings, in fields and 

 grassy ravines. At the former station specimens were trapped near bluffs 

 fully a mile away from the town. These individuals were living in a really 

 wild state; and this was true in winter (January) as well as in the spring 

 and summer. Their numbers were fully as great • as those of the Gambel 

 White-footed Mouse which was present amid the same general surroundings. 



Besides being an aggressive and adaptable species, this mouse is also 

 prolific. It breeds practically throughout the year, has rather large broods, 

 and these may follow one another at relatively short intervals. Adults 

 taken at Snelling in January showed signs of breeding activity; while 



