What kind of animal is the mascot of the Athletics?

In 1904, the Athletics won the AL pennant and the Giants won the NL pennant. Giants' manager John McGraw refused to participate in what would have been the 2nd World Series (the AL Boston Pilgrims defeated the NL Pittsburgh Pirates the year before). His feeble excuse was that the A's were a bunch of "white elephants" (a term that meant "useless"). Undaunted, A's owner/manager Connie Mack decided to make the white elephant the team mascot. Actually, the elephant has appeared as blue, red, and (currently) green on A's uniforms. And, let's not forget that from 1961-1980, the A's mascot was a mule named Charlie O.