The mule deer (Odocoileus hemionus) is a deer indigenous to western North America; it is named for its ears, which are large like those of the mule. There are believed to be several subspecies, including the black-tailed deer. However, some genetic studies have indicated that mule deer may have developed relatively recently through the interbreeding of white-tailed and black-tailed deer, which may have evolved from white-tailed deer thousands of years ago. Unlike the related white-tailed deer...