CALIFORNIA FISH AND GAME 



203 



is for the deer to raise its tail above the horizontal position, usually to a 

 nearly erect position, so that the white under portion is brought plainly 

 in view as the animal runs away. However, in the case of all forms of 

 mule deer the tendency under similar circumstances is to keep the tail 

 down. At times the tail of the frightened mule deer may be twitched 

 back and forth, as the animal runs away, but in the majority of 

 instances the tail is not elevated above the horizontal and there is often 

 no decided movement of this member. After working in a mule deer 

 country, it is always a matter of interest and surprise upon returning 

 to the habitat of the black-tailed deer to note this characteristic differ- 

 ence in behavior. As a matter of fact, in my estimation, it is one of 

 the most conspicuous differences to be noted between living individuals 

 of the two species. Certainly it is one of the best field characters that 

 we have for identifying the two types of deer. 



Fig. 62. Columbian black-tailed, spotted fawns in Yosemite Valley. Note 

 tendency of nearest fawn to raise tail when frightened, a character of black-tailed 

 and not of mule deer. September 17, 1927. Mus. Vert. Zool. No. 5523. 



METATARSAL GLANDS 



The most reliable and distinctive external character that I have 

 been able to find in the genus Odocoileus is the metatarsal gland, which 

 is a dermal structure located on the outer side of the hind leg slightly 

 more than halfway above the center of the long bone that extends from 

 the "knee" or hock, to the hoof. The location of the gland is discern- 

 ible by the coarse, curly character of the hair that laps over it. 



The size (length, in particular) of this gland has been found to be 

 decidedly constant in each of the three forms of common deer found in 

 the United States. In the white-tailed deer, the common species of the 

 eastern United States, and in the western geographic races of this 

 species, the metatarsal gland is very short, approximately one incli in 

 length, and has a broad elliptical form or outline. In the Columbian 



