14 BULLETIX 1091, U. S, DEPARTMEXT OF AGEICULTUEE. { Buil^Na^l, 



nacity toward each other. While three or four individuals may 

 sometimes be trapped at a single mound, more than two are seldom 

 so caught, and most often only one in one night. Trapping on suc- 

 cessive nights at one mound often yields the larger number, j^et in 

 some cases the number is explained by the fact that two or three 

 nearh^ mature young are taken, and the capture of several individ- 

 uals at a single mound can not be taken to indicate that all are from 

 the one den. Our investigations tend strongly to the conclusion that 

 only one adult occupies a mound, except during the period when the 

 young are in the parental (or maternal) den. In the gassing and 

 excavating of 2'o or more mounds we have never found more than one 

 animal in a den, except in one instance, and then the two present 

 were obviously young animals. 



SENSE DEVELOPMENTS. 



Without making special investigations through a study of behavior 

 or other sj^ecial methods, one can speak in only general terms re- 

 garding what appear to be the special sense developments of kangaroo 

 rats. The eyes are large, as is very often the case in nocturnal ani- 

 mals, and when brought out into the bright light of day the rats 

 perhaps do not see well. Yet. if an animal leaves a den which is in 

 process of excavation, and follows one runway, even in bright sun- 

 light, it makes excellent speed to the next opening, often a distance of 

 several yards. Whether this is accomplished chiefly bj- the aid of 

 sight or in large measure by a maze-following ability, such as ex- 

 periments have shown some rodents to have, can not be stated without 

 precise experimentation. Marked ability to follow a maze would 

 not be at all surprising in view of the labyrinthine character of the 

 underground passages Avhich make up the normal habitation. 



When watching beside a mound by moonlight one is impressed with 

 the fact that the rats possess either a very keen sense of hearing or 

 of sight, probably both. The very slightest movement or noise on 

 the part of the observer results, with a timid individual, in an in- 

 stantaneous leap for safety, a disappearance into the burrow so 

 sudden as to be ahnost startling. All attempts to obtain flashlight 

 photographs at the mounds were failures, the animal either having 

 gotten completely out of the field before the light flashed following 

 the pull of the trigger, or leaving merely an indistinguishable blur 

 on the plate as it went, and this in spite of carefully hiding the trigger 

 chain behind a screen. A slight noise accompanying the trigger 

 action gave the alarm in one case, and in another the length of time 

 of the flash was sufficient for the get-away. The marvelous quick- 

 ness of the animal clearlv indicates a remarkablv short reaction time. 



