222 



ANIMAL BIOLOGY 



they are being renewed the horns are covered with a 

 furry skin, or " velvet," which becomes dead or dried 

 when the horns are full grown when it becomes peeled off. 

 Antlers are generally found only in the male, but the 

 reindeer has them in both sexes. Their usual limitation 

 to the male sex may be correlated with the fact that the 

 males employ them frequently in fighting with one 

 another, especially during the breeding season. In the 



FIG. 174. California valley elk. (From a group in the museum of the 

 California Academy of Sciences.) 



United States, deer and the larger related forms, the 

 moose and elk, have rapidly diminished in numbers, and 

 game laws are enacted for their protection from hunters. 

 Related to the deer family are the antelopes which are 

 represented in North America by the beautiful prong- 

 horn antelope of our western plains. Of the hollow- 

 horned ruminants the once abundant but now nearly 



