I 



AiKiRTl OBSERVATIONS ON WHITE-FOOTED MICE 139 



hold, it quickly obtained another. This led me to suspect that it 

 might attach itself to the mother's hair. But the three examin- 

 ations made failed to support this theory. One clung so ten- 

 aciously to the nipple that the blood oozed out on the surface of 

 the teat when the little one was removed. 



The young mice grew rapidly and, at the end of two weeks, 

 they opened their eyes. Their white underparts stood out in 

 bold contrast to the dark backs and sides. An occasional ex- 

 ploration of the mouse home by a little one, undaunted by the 

 presence of an observer, gave evidence of the boldness that is 

 so characteristic of young mice. 



At that time, it was necessary for me to be away for a few 

 days. During my absence, four half-grown House-Mice (Mus 

 musculus) were put in with the White-Footed mice. Upon my 

 return, I was surprised to find that the White-Footed mother 

 had adopted the four strangers, which were twice the size of her 

 own children. Fearing that the occupants would be too numer- 

 ous for the apartment, I allowed only one of the intruders to re- 

 main with the family. For an experiment the other three young 

 House-mice were placed in the nest of a meadow mouse (Micro- 

 tus orchrogaster) that had recently devoured the last of her sev- 

 en little ones, even in the 

 presence of animal food. She 

 immediately pounced upon 

 one and then another, biting 

 them so savagely that they 

 had to be removed at once. 

 The three orphans were 

 carefull tucked away and 

 given food similar to that 

 of the White - Footed 

 mouse. They lived but 

 thirty - six hours ; while 

 the adopted brother, at 

 present writing, (fourteen 

 days later,) is nearly 

 grown, having been nour- 

 ishing during all this time 

 by the milk of the foster 

 mother. 

 These White-Footed mice, which are nocturnal, were rare- 



TOUXG HOUSE-MOUSE ADOPTED BY 

 WHITE-FOOTED MOUSE 



