178 



NORTH AMERICAN FAUNA 



[No. 55 



Distribution and habitat. The whole arid sagebrush Upper Sono- 

 ran plains of eastern Oregon are occupied by these little animals, 

 which also extend in the same sort of country north in eastern Wash- 

 ington and south into Nevada and California and on the east grade 

 into Onychomys leucog aster bremcaudus in Idaho (fig. 34). They 

 are typical desert animals, living in the lowest, hottest, and dryest 

 valleys they can find. 



General habits. These insectivorous and carnivorous little rodents 

 have many of the habits of the weasel family. They are hunters, 

 wanderers, freebooters, apparently never common, and without per- 

 manent homes of their own. They are generally caught in traps 

 set for other animals at any kind of burrow or in trails or long marks 



made by running the 

 heel or toe along the sur- 

 face of the ground to be 

 followed b y inquisitive 

 animals. They evidently 

 frequent and probably 

 appropriate the burrows 

 of other small rodents, 

 driving out or eating the 

 owners at will. Their 

 large front feet and claws 

 suggest digging powers, 

 but the writer has never 

 found burrows that could 

 be attributed to them and 

 suspects that the claws 

 are weapons rather than 

 tools. They are much 

 used in catching and holding their prey and also used in fighting and 

 for defensive purposes. 



In many years of trapping these animals for specimens about all 

 that could be learned of their habits was from the contents of the 

 stomachs of those caught and from the many species of other small 

 animals eaten by them when caught in traps. From captive indi- 

 viduals, however, much concerning their habits and natures has been 

 learned. One taken on the south side of Malheur Lake on August 31, 

 1920, was kept alive for nearly 3 years. He was not afraid from 

 the first but was not so gentle and tame as others kept in captivity. 

 He resented being handled and would bark and nip one's fingers, 

 and if bothered too much, would on rare occasions actually bite. He 

 was exceedingly quick and nimble and not easily caught in the hands, 

 even in his cage. 



While mainly nocturnal, he could see well in any light and came 

 out of his nest box at any time when hungry, or if he heard the foot- 

 fall of an insect or smelled a mouse of some other species. 



He was a keen hunter and often searched his cage for any grass- 

 hopper, cricket, beetle, or scorpion that might be available. He 

 would pounce on them and kill them, even though he did not eat 

 them at the time. A live mouse in his cage was hunted down and 

 cornered, if it could not be captured in the open. He would per- 

 sistently follow its trail, creeping up in the grass, eager, alert, tail 



FIGURE 34. Range of the grasshopper mouse, Ony- 

 chomys leucogaster fuscogriseus, in Oregon. Type 

 locality circled. 



