HETEROMYID^. 157 



a surface shell remains and one breaks through on stqjping there. 

 A horse soon learns' to avoid these burrows, walking being suf- 

 ficiently tiresome in this sandy region without falling into rat- 

 nests. Not all the burrows are excavated to this extent however, 

 many being simple burrows a few feet in length with two en- 

 trances, or with a branch or two. 



In places where much camping is done, such as by springs 

 on the road from one mining camp to another, the Pocket-Rats 

 are in the habit of coming about camp at night to pick up grain 

 scattered by the horses and other food, becoming comparatively 

 tame, as no one harms them. I never knew a dog to catch one, 

 as they get under way very quickly, and vanish in the nearest 

 burrow ; in such places they have many burrows, perhaps for just 

 such emergencies. 



I have kept Desert Pocket-Rats in captivity several times, 

 at one time having two for several months. Some of the habits 

 of these as observed in captivity are worth recording. The first 

 I kept was caught at the type locality in November. At that 

 season food had become scarce and they were hungry and easily 

 trapped. The box trap was set a few yards from' camp ; hearing 

 the door fall I immediately took the animal out and put it in 

 a cage and put some grain in the cage. It was amusing to see 

 the eagerness with which it began filling its pockets. It stuffed 

 them so full that it must have been almost painful. It would 

 not stop to eat, but hunted about for some exit; not finding one 

 it ejected the contents of its pockets in a corner out of the 

 firelight and went back for more. This time it ate a little grain, 

 but soon gathered the remainder and deposited it with the first. 

 After eating a little more it refilled its pockets and hunted about 

 for a better place to make a cache, seeming to think its first 



choice insecure. 



On arriving home I put a little dry earth in the cage. This 

 pleased the Pocket-Rats and they enjoyed a good dust bath, 

 rolling in the earth and pushing along on their bellies. They 

 looked much better for their dust bath, the roughened pelage 

 becoming smooth and glossy. 



