156 ANIMAL LIFE IN THE YO SEMITE 



Only once, in our rather extended and intensive work in the habitat 

 of Aplodontia, did any of our party happen to see one of the animals 

 abroad. On the evening of June 23, 1915, at 7 :05 p.m., one was seen run- 

 ning along the bank of the creek in Indian Canon (northeast of Yosemite 

 Falls). It moved very rapidly, at perhaps 5 feet a second, and its gait 

 was like the lumbering gallop of a bear. At our Lyell Canon camp a 

 month later a specimen of Aplodontia was trapped alive and kept for 

 a while in camp (pi. 31a). 



The manner of life of the mountain beaver is, like its general appear- 

 ance, suggestive of that of the meadow mouse. It frequents, almost without 

 exception, the near vicinity of streams. When the naturalist goes in search 

 of Aplodontia he seeks creek banks bordered by good growths of willow, 

 creek dogwood, and other riparian shrubs and herbs. On the stems of 

 these, marks of gnawings will be in evidence if the animals are present. 

 Also burrows or tunnels in the ground will be found often within but a 

 yard or so of water. These tunnels, like those of meadow mice, are, in 

 general, parallel with the surface of the ground, and have rather frequent 

 openings to the surface. (See fig. 31&.) Within these burrows the animals 

 make their nests, in which they remain during the daytime and within 

 which their young are reared. 



At Chinquapin a series of Aplodontia workings was laid open and 

 mapped by one of our party on June 21, 1915. The tunnels ran partly 

 through rocky ground and partly through humous soil. Close by was the 

 north fork of Indian Creek in which the stream of water was about 2 feet 

 wide and 3 to 6 inches deep. Water was also running through one of the 

 tunnels. The tunnel system, for the most part, was in the bank, about 3 

 feet above the level of the stream. The tunnels averaged between 6 and 7 

 inches (160 mm.) in diameter, the entrances being slightly larger. No 

 nest was found in the series of tunnels opened, but examination of tunnel 

 systems elsewhere has shown the presence of underground nests, so it may 

 be presumed that the animals which made this particular excavation had 

 their nest in some other burrow. The floor of the tunnel system is usually 

 well packed as a result of constant use and is kept clear of debris of every 

 sort so long as the place is occupied by the animals. The set of tunnels 

 at Chinquapin yielded 2 animals, a male and a female, in the several days 

 of trapping prior to the time when the system was dug out. 



Another colony was noted along the East Fork of Indian Caiion (above 

 Yosemite Valley). Here the workings occupied, in 1915, practically all 

 available locations from the crossing of the trail to North Dome northward 

 to the headwaters of the creek. In one place, even during June, the creek 

 practically disappeared from view so great was the amount of water 

 running through the tunnels. Other colonies were found on creeks near 



