246 NOKTH AMERICAN FAUNA [No. 55 



They run on all fours like other mice, and are quick and difficult 

 to capture as they flash from bush to bush. Their tracks are in 

 fours, the large hind feet showing in front of the smaller front feet. 

 In feeding, the hands are used to hold the food and to fill and 

 empty the pockets. They are also used in digging and are provided 

 with strong claws. 



Like all storing animals they are not sociably inclined, and usually 

 but one adult is found in a den. The litter apparently disbands as 

 soon as full grown and each begins storing for itself. In captivity 

 the animals prefer to be solitary, but for a week or more 5 were 

 kept together in a box. They quarreled much of the time and even 

 fought occasionally, and as far as possible each made a separate nest. 

 Sometimes on cold mornings 2 or 3 would be found cuddled up 

 together, but as soon as the weather warmed up they would begin 

 to quarrel and separate. Two males that were taken in a box on a 

 long journey fought until one was killed, its nose and feet being 

 much bitten and the skin over its back punctured with so many 

 small holes from the hind claws of the other that the skin, when 

 removed, looked like a sieve. 



Their discord is clearly caused by the storage habit. Each would 

 fill its cheek pouches with food, then hunt for a safe place to store it, 

 but another was sure to find it and carry it away to some other 

 corner. And thus they would steal from each other all night. One 

 large and one small mouse in a box were given a cup with a hole 

 in each side, so the smaller one could not be cornered in its nest. In 

 the morning all the choice seeds and a grape were stored in the cup 

 and covered with sand and the larger animal was guarding it, while 

 the other had to content itself with rolled oats in a far corner. The 

 storage habit, the selfish greed of gain, seems to destroy all better 

 sentiments of these little animals. 



They show no signs of playfulness with each other, but each 

 greatly enjoys a hollow wheel or an inclined disk, running it by the 

 hour with evident signs of exhilaration. If two got into the wheel 

 together they would quarrel until one got out. 



Their voices are rarely heard when alone, unless one becomes cold 

 or hungry, is held too closely, or is in some way hurt or injured. 

 The complaining squeak, or que^ que, que, is made, varying from a 

 faint whimper to a whine or a shrill squeal, according to circum- 

 stances. When two or more are together their que, que note is often 

 heard as they meet and scold, threaten, fight, or try to get each 

 other's stores or as one disturbs another in his nest. They seem to 

 have no pleasant conversational notes. 



Hibernation. The pocket mice do not become excessively fat in 

 autumn, but with the aid of their stored food supply they seem to 

 keep within their burrows during the cold winter weather, and 

 not improbably spend a part of the time in partial or complete 

 hibernation. 



Breeding habits. The females have 3 pairs of mammae 2 in- 

 guinal and 1 pectoral. The number of embryos recorded varies 

 from 3 to 5. The young are born at irregular times during sum- 

 mer, but there seems to be no data to indicate more than one litter 

 in a season. 



