.1919] Dixon: Bushy-tailed Wood Rats of California 59 



individual which the author kept captive, the posture of the body was 

 often cony-like, especially when the animal sat hunched up in a crevice 

 in the rock with its ears held upright in a watchful attitude such as is 

 illustrated by plate 3, figure 5. In this individual, which was imma- 

 ture, the fringe of hairs on each side of the tail had not yet reached 

 full development. Ordinarily the tail was carried trailed out behind, 

 and although this member was often waved back and forth sidewise 

 it was never seen curved forward over the back in squirrel or chip- 

 munk fashion. Watch was kept to see if any special function or use 

 was made of the bushy tail but none was discovered. The gait of the 

 animal was decidedly rat-like, being a scamper or run and not a series 

 of hops or hobbles such as characterizes the manner in which a rabbit 

 or cony progresses. 



The bushy-tailed wood rats are robust animals, stronger, heavier 

 boned and with greater muscular development in both fore and hind 

 limbs than is found in their round-tailed cousins of the lowlands. 

 Typical adult specimens of N. c. cinerca from the central Sierra 

 Nevada have an average body length of 225 mm. (8% inches), with 

 the tail about 162 mm. (6% inches) long, giving a total length of 

 387 mm. (151/4 inches). Such animals weigh about 357 grams (12 

 ounces). 



TIMIDITY AND EEFLEXES 



Bushj^-tailed wood rats are alert, vigorous animals. Some idea of 

 the relative speed of nervous impulses in an individual of this species 

 may be had from the following account of experiences. A camera was 

 placed with the lens within thirtj' inches of a rat in the open under 

 ordinary ovitdoor conditions. All moving parts of the shutter of the 

 camera were then covered and three exposures of l^ 5 of a second made 

 while the animal was sitting still. In one case, development of the 

 plate showed that the animal moved during the exposure. In the 

 other two cases, the first and third exposures, no motion was noticeable. 



In similar trials upon other small rodents it was found that when 

 the exposures were made as indicated below, little or no movement 

 could be detected in the resulting negatives. In other words, the 

 impulse of the animal to jump (such impulse being caused by the 

 audible click of the shutter) w^as not carried out during the short 

 interval that the shutter was open. After repeated clicking of the 

 shutter certain individuals became accustomed to the sound and 



