FIELD BOOK OF MAMMALS 



the House Mouse. The former is much more attractive and 

 is quickly recognized by the white underparts, white feet, 

 well-haired tail, and general color pattern of contrasted upper 

 and lower parts. These distinctions are not quite as obvious 

 for some of the desert species of Peromyscus, such as eremicus, 

 but a little experience soon familiarizes one with the general 

 appearance of this genus and it will not be confused with the 

 introduced Mus musculus. 



White-footed Mice range from sea-level, or below it (Death 

 Valley), to the limits of plant growth on the crests of the 

 mountain ranges, and from regions of heavy annual precipi- 

 tation to the most arid deserts. Allowing for the changes 

 in color pattern we have learned to expect, the Mouse shows 

 some other differences that may obscure its identity. The 

 forms from the regions of heavy rainfall are dark, nearly 

 black; those from the rainless deserts are very pale; some of 

 the most specialized have developed large size {californicus) or 

 large ears (truei), but they are all members of the same large 

 group of closely related species. The food of all species is 

 almost strictly vegetarian, and while White-footed Mice eat 

 grain and the seeds of timothy and pasture grasses, they sel- 

 dom make serious inroads on crops and are not the economic 

 problem that the Meadow Mice are. Most species of White- 

 footed Mice prefer more cover than they find in a cultivated 

 field and therefore confine their depredations to the margins 

 of the field that meet with undisturbed terrain. 



White-footed Mice have interesting habits and make attrac- 

 tive pets; they are gentle and tame quickly. Besides the 

 "squeak" characteristic of most Mice, some of the species of 

 Peromyscus have been heard to sing in a fine, high-pitched 

 trill, not unlike a canary. 



The number of young in a litter varies from three to seven 

 but is usually four or five. These Mice may have as many as 

 four litters a year, hence young may be seen at almost any 

 time. Seton has noted the appearance of the first brood as 

 April 1st in Manitoba; in warmer regions it would be earlier. 



Genus Oryzomys' 

 Dentition: Incisors, {; Canines, g; Premolars, §; Molars, f = i6. 



^ See E. A. Goldman, North American Fauna, No. 43, 1918, for an 

 extensive review of the North American forms of this large genus. 



