Water for Elephants main characters?

-I know Jacob, Marlena, and August are main characters, but I'm not sure where exactly to draw the line between main characters and supporting characters. Would Uncle Al, Camel, Walter, Rosemary and Rosie be main characters too?Uncle Al, Camel, Walter, and Rosemary are definitely supporting characters. Rosie might be elevated to a main character, just because she's a big part of the story.