148 NORTH AMERICAN FAUNA [No. 55 



the day. The note varies with circumstances, seeming at times 

 unemotional, but in the face of imminent danger being sharp and 

 forceful, and even crowded into a wild, blended chirrrrr as one is 

 surprised by an enemy, or even into a shriek of alarm at a narrow 

 escape. Each takes its turn at calling or occasionally reports its 

 presence by a few short chirps, while feeding. 



Feeding and preparing deep burrows and warm nests for winter 

 are their principal summertime activities. New burrows are dug or 

 the old ones deepened and extended, and before cold weather begins 

 dry grass is carried in for big warm nests. A new burrow is gen- 

 erally simple, with a front door w r here all the earth is thrown out, and 

 a concealed back door some 10 or 15 feet distant. The nest cavity 

 is usually 2 or 3 feet below the surface of the ground and large 

 enough for a big nest a little above the lowest part of the tunnel. 

 Several smaller cavities and short side tunnels are generally dug for 

 sanitary and unknown purposes. Old dens that have been used for 

 many years are often more elaborate with many openings and several 

 nest cavities and numerous other cavities and side tunnels. 



Hibernation. Apparently the old males, which are the first to be- 

 come very fat, enter hibernation about the last of July; the others 

 follow as soon as their skins are well lined with fat. By August 

 15 most of the squirrels have disappeared into their burrows, but up 

 to the middle of September, especially at higher elevations, half- 

 grown young from late litters occasionally are found active, busily 

 stuffing their large stomachs with seeds and forage in an effort to 

 accumulate the fat necessary to carry them through the winter. 

 In the spring of 1919 Cantwell caught the first one at Wallowa Lake 

 on April 13, one that had appeared through 6 inches of snow. By 

 April 18 they were common in warm grassy places among the 

 yellow pines. The large ones were still very fat, but some small 

 ones were poor, with the skin clinging tight to the flesh. On April 

 28 he found them abundant at Sled Springs and over the Imnaha 

 Plateau, where they had appeared about April 20. These localities 

 are in the middle elevations of their range. Higher and lower 

 the hibernation dates may vary somewhat. 



Breeding Tidbits. According to W. T. Shaw, who has made an 

 intensive study of these squirrels, the mating season begins shortly 

 after they come out of hibernation. The period of gestation is 24 

 days. The naked, blind, and toothless young grow rapidly and begin 

 to open their eyes on the seventeenth day and to come out of the 

 burrows when 21 to 24 days old. Shaw (1925, p. 108) gives 5 as 

 the average number of young in a litter. The mammae of the fe- 

 males are arranged in 5 pairs 1 inguinal, 2 abdominal, and 2 

 pectoral borne on 4 separate mammary glands. 



Food habits. In early spring young green plants, roots, and bulbs 

 form most of the food of these squirrels. With the store of fat left 

 over from the fall, these carry them through the mating season. 

 As soon as the early flowers appear the squirrels eat them. Later 

 the green and ripening seeds of a great variety of native, intro- 

 duced, and cultivated plants form most of the food. Berries and 

 grasshoppers, caterpillars, and other insects are eaten to a slight ex- 

 tent, but toward fall the ripe seeds and grains are especially sought 

 and the large stomachs are distended with the richest food available. 



