PRAIRIE WHITE-FOOTED MOUSE 75 



the Mus leucopus [White-footed mouse] this species never appears 

 to be gregarious. . . . 



' ' I have found the young in March and April, and observed two 

 females, each with five young, apparently but a few days old, about 

 the tenth of November, while they are found in every intervening 

 month. In nearly every instance within my observation the number 

 of young produced at a birth has been five. I once found six, and 

 have at times, though rarely, seen three or four. The young are 

 attached to the teats, as in the species last described ; and a female 

 was seen to carry five for several rods in this way, jumping along 

 rapidly despite their weight. As soon as they are able to take care 

 of themselves, the young leave the mother. In summer, I have sev- 

 eral times found one apparently but a few weeks old, living 'alone 

 in a nest made by himself. In spring, I have always found the old 

 male living with the female and young; but during the summer, I 

 have sometimes observed the male leading a solitary life, and the 

 females and young in burrows by themselves. The food of this 

 mouse, on the prairies, appears to be herbaceous plants, with their 

 seeds ; but I have been unable to see that it ever digs for roots. It 

 is interesting to observe that this, like the Mus leucopus, seeks its 

 food on the top of the ground, running on the snow in winter in 

 search of seeds, and collecting them in autumn instead of roots, 

 when it travels as often by springing over the grass as by running 

 through it. This mouse probably feeds more or less upon insects, 

 as it is carnivorous in captivity; though some specimens are much 

 less so than others." 13 



On November 10, 1917, the writer received from Yinton an adult 

 female example of this form along with four young apparently less 

 than a week old. The latter were scantily haired and had the eyes 

 closed. This family was found in a burrow about five inches deep 

 in the soil. No evidences of stored food were found in the burrow. 

 The measurements of the young are as follows : 



TOTAL TAIL HIND 



LENGTH TERTEBE^ FOOT 



Specimen No. 1 64 mm. 22 mm. 11 mm. 



Specimen No. 2 60 mm. 23 mm. 11 mm. 



Specimen No. 3 61 mm. 20 mm. 11 mm. 



Specimen No. 4 60 mm. 20 mm. 11 mm. 



NOTE Since the specimens were so small the measurements are given 

 in millimeters instead of fractions of an inch. 



13 Hoy & Kennicott, in Kennieott, Agr. Kept, for 1856, U. S. Patent Office 

 Kept., 93-94, 1857. 



