16 BULLETIN 1091, U. S. DEPAETMEXT OF AGPJCULTUKE. { bu1?.^Xo!'i, 



is maturing the animal's activities appear to be concentrated on tiiis 

 work. During September. 1919. when a good crop of grass seed was 

 rij^ening following the summer rains, a kangaroo rat under observa- 

 tion made repeated roimd trips to the harvest field of gi-ass heads. 

 Each outward trip occupied from 1 to 1^ minutes, while the unload- 

 ing trip into the burrow took only 15 to 20 seconds. 



One individual in a laboratory cage, which had not yet been given 

 a nest box, busied itself in broad daylight in carrying its grain supply 

 into the darkest corner of the cage. When a nest box is supplied the 

 individual will retreat into its dark shelter, and will only come forth 

 after darkness has fallen unless forcibly ejected, but will store the 

 food supplied. 



In another case an animal escaped while being handled, and sought 

 refuge behind a built-in laboratory table, where it could not be re- 

 covered without tearing out the table. For four days and nights it 

 had the run of the laboratory. On the first night of its freedom it 

 found and entered a burlap bag of grass seed that had been taken 

 from a mound. A trail of seed and chaff next morning showed that 

 it had been busily engaged in making its new cjuarters comfortable 

 with bedding and food. After four nights of freedom it was cap- 

 tured alive in a trap, and later it was found that it had moved from 

 the corner behind the table to the space beneath a near-by drawer, 

 where it had stored about 2 quarts of the gi'ass seed and a handful of 

 the oatmeal used for trap bait. 



BREEDING HABITS. 



Observations on breeding habits have consisted mainly in taking 

 records from the females trapped at all seasons of the year through- 

 out the course of the investigation, and from examinations made dur- 

 ing poisoning operations, and yet from this source the number of 

 pregnant females taken or of young discovered is disappointingly 

 small. The records indicate a breeding period of considerable length, 

 extending from January to August, inclusive. It is possible that the 

 length of the period may be increased by a second litter from the 

 earliest breeding females in summer, but the large percentage of 

 nonpregnant or nonbreeding animals which occurs throughout the 

 season would indicate a wide variation in the time of breeding of 

 different individuals. 



Trapping in February and March for the purpose of securing 

 greater numbers of female specimens, begun with the idea that these 

 months were most likely to be the breeding months, has invariably 

 yielded an unsatisfactory number of nonbreeding specimens and 

 males. Unfortunately, the numbers of females secured in some 

 months were not sufficient to be significant if worked out in per- 



