CALIFORNIA FISH AND GAME 219 



when the deer is bothered by flies. This twitching of the tail is per- 

 haps a nervous reflex manifestation, since I have frequently noted the 

 tails of mule deer being twitched violently when the only flies around 

 the deer were buzzing around the animals' forelegs. This twitching 

 of the tail, under such circumstances, is frequently accompanied by a 

 violent stamping of the forefeet and perhaps is merely a method of 

 expressing irritation. 



As bearing on the position in which the tail is carried in the 

 frightened mule deer, I wish to cite the following incident which I have 

 found to be the typical reaction of mule deer in California. December 

 8, 1927, in Yosemite Valley, I observed two adult mule deer that were 

 badly frightened. They ran with tails held straight down, and in this 

 instance the tails M'ere not twitched back and forth across the white 

 rump patches as is sometimes the case. 



SENSES 



Sight. 



The sense of sight is highly developed in the mule deer, being some- 

 what better, in my estimation, than that of the black-tailed deer. This 

 may be due in part to the more open character of the mule deers' 

 habitat. 



Not only are mule deer able to see well during daylight hours but 

 their eyes are especially effective during the dim lighting of early morn- 

 ing and late evening. Because of the limitations of the human eye, I 

 have been unable to ascertain just how effective the sight of deer may 

 be at night, but I have repeatedly found under such circumstances that 

 the eyesight of deer was very much keener than my own. If I may be 

 allowed a photographic comparison. I would say that the eye of the 

 mule deer at night may be compared to an f 4.5 lens, while the human 

 eye would not rate higher than an f 6.8 lens. 



As with most other large game mammals, the sight of deer is not 

 particularly keen or analytical as regards stationary objects. This has 

 been proven many times by different individuals who, when clad in 

 neutral colored (khaki) clothes, have remained stationary against a 

 neutral background and have had deer walk up to within fifteen or 

 twenty feet of them without detecting their presence so long as the 

 human observers remained motionless and so long as there was no 

 telltale breeze blowing from the observers toward the deer. However, 

 the least movement, such as the mere twitching of a finger or slight 

 movement of the hand, has been found sometimes in such instances to 

 be immediately detected by the deer, which, without the slightest hesi- 

 tation, would immediately dash away. 



There is considerable question in my mind, owing to various field 

 experiences, that the mule deer is able to identify definitely a strange 

 object at a distance. The extreme wariness of certain old mule deer 

 bucks that resort to instant flight the moment they detect the moving 

 figure of the hunter on the skyline, at a distance of two or three hundred 

 yards, I believe in many cases to be merely an instinctive reaction to 

 flee from the presence of any suspicious moving object. In short. I do 

 not believe that in such cases the deer always recognizes the identity of 

 the moving form. 



