X is for Fox (Only if it is spelled backwards)
I know. Fox starts with 'F'. I just couldn't find a Yellowstone animal whose name started with 'X' so I had to cheat. Sorry about that!
Did You Know?
Prior to the establishment of the National Park Service, the U.S. Army protected Yellowstone between 1886 and 1918. Fort Yellowstone was established at Mammoth Hot Springs for that purpose.