288 



NORTH AMERICAN FAUNA 



(No. 55 



from Arizona and New Mexico to southeastern British Columbia, 

 and west to the eastern slope of the Sierra Nevada and Cascade 

 Ranges (fig. 66). In the Columbia and Snake River Valleys they are 

 as small or smaller than typical arizonensis, while in the higher 

 valleys of the Great Basin they are almost as large and as pale as 

 longicaudus of the Great Plains region. In fact the specimens from 

 eastern Oregon could be sorted into longicaudus, arizonensis, and 

 oribasus with many intermediates between these forms. Until more 

 thorough study of the group can be made it seems best to refer the 

 weasels of this group in eastern Oregon to arizonensis. They range 

 from the lowest valleys to high up in the mountains, wherever food 

 is available. 



General habits. These bold and savage little hunters cover much 

 of the country in search of prey, ranging widely until good hunting 

 is found and then killing and feasting on the fat of the land until 



game becomes scarce and 

 they are urged by hunger 

 or wanderlust to move on. 

 Usually they are seen run- 

 ning from one burrow to 

 another in the open, or 

 along fences or logs where 

 small mammals live, or 

 are caught in traps in the 

 burrows of ground squir- 

 rels, pocket gophers, kan- 

 garoo rats, wood rats, 

 mountiain beavers or in 

 winter in traps set and 

 baited for marten and 

 mink. Their little paired 

 tracks, widely spaced over 

 the snow, are unmistak- 

 able and, either in long curving lines or intricate network of cross 

 lines, show a well-written record of the hunt for small game. 



Breeding habits. Fortunately for other forms of small animal 

 life weasels are not very prolific. The females have, 5 or 6 pairs of 

 mammae close together on the posterior part of the abdomen, and 

 the litter probably numbers 5 or 6. When about half grown the 

 young are sometimes found following the mother. More often, 

 though, weasels are found alone even in the breeding season, and it 

 seems probable that they do not breed with much regularity ; other- 

 wise there would be a greater increase in numbers. 

 Food habits. The food of these weasels consists largely of mice, 



fpphers, ground squirrels, wood rats, young rabbits, and occasionally 

 irds. When game is abundant they eat the blood and some choice 

 parts and often kill far more than they can make good use of, appar- 

 ently for the pleasure of killing. Their slender form enables them to 

 enter burrows of such small animals as ground squirrels and pocket 

 gophers and capture the occupants, feast upon them, and then use 

 their nests and burrows as comfortable homes. The young of such 

 animals as well as the adults, trapped without possibility of escape, 



FIGURE 66. Range of Cascade and Arizona weasels 

 in Oregon : 1, Mustela longioauda saturate; 2, M. I. 

 arizonensis. Type locality circled. 



